Sheet beam-type testing apparatus

ABSTRACT

An electron beam apparatus such as a sheet beam based testing apparatus has an electron-optical system for irradiating an object under testing with a primary electron beam from an electron beam source, and projecting an image of a secondary electron beam emitted by the irradiation of the primary electron beam, and a detector for detecting the secondary electron beam image projected by the electron-optical system; specifically, the electron beam apparatus comprises beam generating means  2004  for irradiating an electron beam having a particular width, a primary electron-optical system  2001  for leading the beam to reach the surface of a substrate  2006  under testing, a secondary electron-optical system  2002  for trapping secondary electrons generated from the substrate  2006  and introducing them into an image processing system  2015 , a stage  2003  for transportably holding the substrate  2006  with a continuous degree of freedom equal to at least one, a testing chamber for the substrate  2006 , a substrate transport mechanism for transporting the substrate  2006  into and out of the testing chamber, an image processing analyzer  2015  for detecting defects on the substrate  2006 , a vibration isolating mechanism for the testing chamber, a vacuum system for holding the testing chamber at a vacuum, and a control system  2017  for displaying or storing positions of defects on the substrate  2006.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.11/360,704, which is a Continuation of U.S. application Ser. No.09/891,612, filed Jun. 27, 2001, which claims the priority of JapaneseApplication Nos. 2000-227132; 2000-335756; 2000-374164; 2001-22931;2001-31901; 2001-31906; 2001-33599; 2001-36088; 2001-68301; 2001-115013and 2001-158662 filed on Jul. 27, 2000; Nov. 2, 2000; Dec. 8, 2000; Jan.31, 2001; Feb. 8, 2001; Feb. 8, 2001, Feb. 9, 2001; Feb. 13, 2001; Mar.12, 2001; Apr. 13, 2001 and May 28, 2001 (respectively) all of which areincorporated herein by reference.

TECHNICAL FIELD

In semiconductor processes, design rules are now going to enter the eraof 100 nm, and the production scheme is shifting from small-kind massproduction represented by DRAM to a multi-kind small production such asSOC (silicon on chip). Associated with this shifting, the number ofmanufacturing steps has been increased, and an improved yield of eachprocess is essential, so that testing for defects caused by the processbecomes important. The present invention relates to a charged particlebeam suitable for a sheet beam based testing apparatus for testing awafer after each of steps in a semiconductor process, and moreparticularly, to a sheet beam based testing apparatus using a chargedparticle beam such as an electron beam, and a semiconductor devicemanufacturing method and an exposure method using the testing apparatus.

BACKGROUND ART

With the trend of increasingly higher integration of semiconductordevices and finer patterns, a need exists for high resolution, highthroughput testing apparatuses. A resolution of 100 nm or less isrequired for examining defects on a wafer substrate of 100 nm designrule. Also, as the amount of testing is increased to cause an increasein manufacturing steps resulting from higher integration of devices, ahigher throughput is required. Further, as devices are formed of anincreased number of layers, testing apparatuses are required to have theability to detect defective contacts (electric defect) of vias whichconnect wires between layers. While optical defect testing apparatusesare mainly used at present, it is anticipated that electron beam baseddefect testing apparatuses will substitute for optical defect testingapparatus as a dominant testing apparatus in the future from a viewpointof the resolution and defective contact testing capabilities. However,the electron beam based defect testing apparatus also has a disadvantagein that it is inferior to the optical one in the throughput.

For this reason, a need exists for the development of a high resolution,high throughput testing apparatus which is capable of detecting electricdefects. It is said that the resolution of an optical defect testingapparatus is limited to one half of the wavelength of used light, andthe limit is approximately 0.2 μm in an example of practically usedoptical defect detecting apparatus which uses visible light. On theother hand, in electron beam based systems, scanning electronmicroscopes (SEM) have been commercially available. The scanningelectron microscope has a resolution of 0.1 μm and takes a testing timeof eight hours per 20 cm wafer. The electron beam based system also hasa significant feature that it is capable of testing electric defects(broken wires, defective conduction, defective conduction of vias, andso on). However, it takes so long testing time that it is expected todevelop a defect testing apparatus which can rapidly conduct a test.

Generally, a testing apparatus is expensive and low in throughput ascompared with other process apparatuses, so that it is presently usedafter critical steps, such as after etching, deposition, CMP(chemical-mechanical polishing) planarization processing, and so on.Now, describing a testing apparatus in accordance with an electron beambased scanning (SEM) scheme, an SEM based testing apparatus narrows downan electron beam which is linearly irradiated to a sample for scanning.The diameter of the electron beam corresponds to the resolution. On theother hand, by moving a stage in a direction perpendicular to adirection in which the electron beam is scanned, a region underobservation is tow-dimensionally irradiated with the electron beam. Thewidth over which the electron beam is scanned generally extends overseveral hundred μm. A secondary electron beam generated from the sampleby the irradiation of the narrowed electron beam (called the “primaryelectron beam”) is detected by a combination of a scintillator and aphotomultiplier (photomultiplier tube) or a semiconductor based detector(using PIN diodes). The coordinates of irradiated positions and theamount of the secondary electron beam (signal strength) are combined togenerate an image which is stored in a storage device or output on a CRT(Braun tube).

The foregoing is the principle of SEM (scanning electron microscope).From an image generated by this system, defects on a semiconductor(generally, Si) wafer is detected in the middle of a step. A scanningspeed, corresponding to the throughput, is determined by the amount ofprimary electron beam (current value), diameter of the beam, and aresponse speed of a detector. Currently available maximum values are 0.1μm for the beam diameter (which may be regarded as the same as theresolution), 100 nA for the current value, and 100 MHz for the responsespeed of the detector, in which case it is said that a testing speed isapproximately eight hours per wafer of 20 cm diameter.

In the SEM based testing apparatus described above, the cited testingspeed is considered substantially as a limit. Therefore, a new scheme isrequired for increasing the testing speed, i.e., the throughput.

DISCLOSURE OF THE INVENTION

The present invention relates to an electron beam apparatus suitable fora sheet beam based testing apparatus, and a semiconductor devicemanufacturing method and an exposure method using the apparatus.

A first embodiment of the present invention provides a map projectiontype electron beam apparatus. For this purpose, the first embodimentprovides a substrate testing apparatus, a substrate testing method and adevice manufacturing method using such a substrate testing apparatus,characterized by comprising:

beam generating means for irradiating an electron beam having aparticular width;

a primary electron-optical system for leading the charged particle beamto reach the surface of a substrate under testing;

a secondary electron-optical system for trapping a secondary electronbeam generated from the substrate and leading the same to an imageprocessing system;

a stage having for transportably holding the substrate with a continuousdegree of freedom equal to at least one;

a testing chamber for the substrate;

a substrate transport mechanism for transporting the substrate into andout of the testing chamber;

an image processing analyzer for detecting defects on the substrate;

a vibration isolation mechanism for the testing chamber;

a vacuum system for holding the testing chamber at a vacuum; and

a control system for displaying or storing positions of defects on thesubstrate.

A second embodiment of the present invention provides an electron beamapparatus suitable for a testing apparatus for testing an object undertesting by irradiating the object with an electron beam, and a devicemanufacturing method using the electron beam apparatus.

A second embodiment of the present invention provides a testingapparatus comprising:

an electron-optical device having an electron-optical system forirradiating the object under testing with a primary electron beam froman electron source to project an image of secondary electrons emitted bythe irradiation of the primary electron beam, and a detector fordetecting the secondary electron image projected by the electron-opticalsystem;

a stage device for holding the object under testing and moving theobject under testing relative to the electron-optical system;

a mini-environment device for supplying a clean gas to the object undertesting to prevent dust from attaching to the object under testing;

a working chamber for accommodating the stage device, said workingchamber being controllable in a vacuum atmosphere;

at least two loading chambers disposed between the mini-environmentdevice and the working chamber, and adapted to be independentlycontrollable in a vacuum atmosphere;

a loader having a carrier unit capable of transferring the object undertesting between the mini-environment device and one of the loadingchambers, and another carrier unit capable of transferring the objectunder testing between the one loading chamber and the stage device; and

a vibration isolator through which the working chamber and the loadingchamber are supported.

Further, the second embodiment of the present invention provides atesting apparatus comprising:

an electron-optical device having an electron-optical system forirradiating the object under testing with a primary electron beam froman electron source, and for accelerating secondary electrons emitted bythe irradiation of the primary electron beam with a decelerationelectric field type objective lens to project an image of the secondaryelectrons, a detector for detecting the secondary electron imageprojected by the electron-optical system, and electrodes disposedbetween the deceleration electric field type objective lens and theobject under testing for controlling a field intensity on the surface ofthe object under testing which is irradiated with the primary electronbeam;

a stage device for holding the object under testing and moving theobject under testing relative to the electron-optical system;

a working chamber for accommodating the stage device, said workingchamber being controllable in a vacuum atmosphere;

a loader for supplying the object under testing onto the stage devicewithin the working chamber;

a precharge unit for irradiating a charged particle beam to the objectunder testing placed in the working chamber to reduce variations incharge on the object under testing;

a potential applying mechanism for applying a potential to the objectunder testing; and

a supporting device supported through a vibration isolator forsupporting the working chamber.

In the testing apparatus described above, the loader may include a firstloading chamber and a second loading chamber capable of independentlycontrolling an atmosphere therein, a first carrier unit for carrying theobject under testing between the first loading chamber and the outsideof the first loading chamber, and a second carrier unit disposed in thesecond loading chamber for carrying the object under testing between thefirst loading chamber and the stage device. The electron beam apparatusmay further comprise a partitioned mini-environment space for supplyinga clean gas flowing to the object under testing carried by the loader toprevent dust from attaching to the object under testing, wherein thesupporting device may support the loading chamber and the workingchamber through the vibration isolator.

Also, the testing apparatus may further comprise an alignment controllerfor observing the surface of the object under testing for an alignmentof the object under testing with respect to the electron-optical systemto control the alignment, and a laser interference range finder fordetecting coordinates of the object under testing on the stage device,wherein the coordinates of the object under testing is determined by thealignment controller using patterns formed on the object under testing.In this event, the alignment of the object under testing may includerough alignment performed within the mini-environment space, andalignment in XY-directions and alignment in a rotating directionperformed on the stage device.

Further, the second embodiment of the present invention provides amethod of manufacturing a device comprising the step of detectingdefects on a wafer using the foregoing testing apparatus in the middleof a process or subsequent to the process.

A third embodiment of the present invention provides an electron beamapparatus for focusing electron beams emitted from a plurality ofelectron beam sources on the surface of a sample through anelectron-optical system, characterized by comprising:

a partition wall for separating the electron beam sources from theelectron-optical system, wherein the partition wall has holes in a largeaspect ratio for the electron beams to pass therethrough.

The holes are provided two or more for each of the electron beamsources. Each of the holes is formed at a position which swerves fromthe irradiating axis of the beam source. Preferably, the partition wallis formed of a material having a high rigidity, and the electron beamsource and the electron-optical system are attached to the partitionwall.

The third embodiment of the present invention also provides a devicemanufacturing method for evaluating a wafer in the middle of a processusing the electron beam apparatus.

A fourth embodiment of the present invention provides an evaluationapparatus for directing an electron beam into a sample using anelectrostatic optical system including an electrostatic lens, detectinga secondary electron beam generated from the sample by the irradiationof the electron beam to form data, and evaluating the sample based onthe data, characterized in that:

electrodes in the electron-optical system are coated with a metal havinga work function of 5 eV or higher.

According to this evaluation apparatus, since the electrodes or some ofthe electrodes are coated with a metal having a work function of 5 eV orhigher, no secondary electron beam will be emitted from the electrodes,a discharge will be less likely to occur between electrodes, and abreakdown will occur between electrodes less frequently.

Preferably, the metal coated on the electrodes in the electrostaticoptical system is platinum or an alloy which includes platinum as a mainmaterial. In this case, as the electrodes or some of the electrodes arecoated with platinum (work function: 5.3 [eV]) or an alloy whichincludes platinum as a main material, a smaller amount of secondaryelectron beam will be emitted from the electrodes, so that a dischargewill be less likely to occur between the electrodes, and a breakdownwill occur between electrodes less frequently. Also, even with thesample being a semiconductor wafer, the platinum coated on theelectrodes, if attached on a pattern of the semiconductor wafer, willnot deteriorate transistors, so that it is suitable for testing asemiconductor wafer.

The fourth embodiment of the present invention provides an evaluationapparatus for directing an electron beam into a sample using anelectrostatic optical system including an electrostatic lens, detectinga secondary electron beam generated from the sample by the irradiationof the electron beam to form data, and evaluating the sample based onthe data, characterized in that:

the electrostatic lens includes at least two electrodes having potentialdifferences, and insulating materials positioned between the twoelectrodes for holding the at least two electrodes;

at least one of the at least two electrodes has a first electrodesurface having a minimum inter-electrode distance between the at leasttwo electrodes, a second electrode surface having an inter-electrodedistance longer than the first electrode surface, and a step between thefirst electrode surface and the second electrode surface in a directionalong the at least two electrodes; and

the insulating material substantially vertically supports the secondelectrode surface and an electrode surface of the other electrodebetween the at least two electrodes, and a minimum creeping distance ofthe insulating material between the at least two electrodes issubstantially equal to an inter-electrode distance in the supportedelectrode portion.

According to this evaluation apparatus, the electrodes are supported bythe insulating material which has long creeping distance, so that adischarge between electrodes, and hence a breakdown between electrodescan be made less probable. Further, at least one of the electrodes isshaped to have the first electrode surface, the second electrode surfaceand the step between these electrode surfaces, so that the surface ofthe insulating material need not be formed with crimps, resulting in alower manufacturing cost.

Also, since the minimum creeping distance of the insulating materialbetween the electrodes is substantially equal to the distance betweenthe electrodes in the supported electrode portion, the surface of theinsulating material is substantially free from ruggedness between theelectrodes, and a gas exhausted from the insulating material will not beincreased. Therefor the degree of vacuum will not be lowered in a beampath of the apparatus.

Preferably, the metal coated on the electrodes in the electrostaticoptical system is platinum or an alloy which includes platinum as a mainmaterial. In this case, as the electrodes or some of the electrodes arecoated with platinum or an alloy which includes platinum as a mainmaterial, a discharge between electrodes, and hence a breakdown betweenelectrodes will occur less frequently. Also, even with the sample beinga semiconductor wafer, the platinum coated on the electrodes, ifattached on a pattern of the semiconductor wafer, will not deterioratetransistors, so that it is suitable for testing a semiconductor wafer.

Further, the fourth embodiment of the present invention also provides adevice manufacturing method using the evaluation apparatus,characterized by evaluating patterns on a semiconductor wafer, which isthe sample, using the evaluation apparatus in the middle of devicemanufacturing.

According to this device manufacturing method, by using the evaluationapparatus in the middle of device manufacturing, even if patterns on thesemiconductor wafer, which is a sample, are evaluated, the evaluationcan be made without breakdown between electrodes in the electrostaticoptical system.

A fifth embodiment of the present invention provides an electron beamapparatus for irradiating a sample with a primary electron beam using aprimary optical system, and separating a secondary electron beam emittedfrom the sample from the primary optical system by an ExB separator forintroduction into a secondary optical system, characterized in that:

the amount of deflection of the secondary electron beam by a magneticfield of the ExB separator is twice the amount of deflection by anelectric field, and the direction of deflection by the magnetic field isopposite to the direction of deflection by the electric field.

This electron beam apparatus is characterized in that, in the electronbeam apparatus for irradiating the sample with the primary electron beamusing a primary optical system, and separating the secondary electronbeam emitted from the sample from the primary optical system by the ExBseparator for introduction into the secondary optical system, the amountof deflection of the secondary electron beam by the magnetic field ofthe ExB separator is twice the amount of deflection by an electricfield, and the directions of deflection are opposite to each other.

The fifth embodiment of the present invention also provides an electronbeam apparatus for irradiating a sample with a primary electron beamusing a primary optical system, and separating a secondary electron beamemitted from the sample from the primary optical system by an ExBseparator for introduction into a secondary optical system,characterized in that the amount of deflection of the primary electronbeam by a magnetic field of the ExB separator is twice the amount ofdeflection by an electric field, and the direction of deflection by themagnetic field is opposite to the direction of deflection by theelectric field.

This electron beam apparatus is characterized in that the amount ofdeflection of the first electron beam by the magnetic field of the ExBseparator is twice the amount of deflection by the electric field, andthe directions of deflection are opposite to each other in the electronbeam apparatus for irradiating the sample with the primary electron beamusing a primary optical system, and separating the secondary electronbeam emitted from the sample from the primary optical system by the ExBseparator for introduction into the secondary optical system.

In this event, preferably, the primary electron beam comprised of aplurality of beams is formed by the primary optical system forirradiating the surface of the sample, and secondary electron beamsemitted from the samples by the irradiation of the primary electron beamcomprised of the plurality of beams are detected by a plurality ofsecondary electron beam detectors.

The aforementioned electron beam apparatus can be available in any of adefect testing apparatus, a line width measuring apparatus, an alignmentaccuracy measuring apparatus, and a high time resolution potentialcontrast measuring apparatus.

Also, the fifth embodiment of the present invention provides a devicemanufacturing method for testing a wafer in the middle of a processusing the electron beam apparatus.

A sixth embodiment of the present invention provides an electron beamapparatus, characterized by comprising:

a measuring mechanism for measuring first data indicative of rising of asecondary charged particle beam signal waveform when a pattern edgeparallel in a first direction is moved in a second direction in regardto an excitation voltage of an objective lens, and second dataindicative of rising of the secondary charged particle beam signalwaveform when a pattern edge parallel in the second direction is movedin the first direction;

means for approximating each of the first data and the second data usingquadratics, finding an excitation condition for the objective lensindicative of a minimum value of each quadratic; and

means for fitting the objective lens to an algebraic mean of the foundexcitation condition.

A plurality of the electron beam apparatuses may be positioned oppositeto the sample such that respective ones of the plurality of primaryelectron beams are converged by corresponding ones of the objective lenssimultaneously on different locations on the sample.

Further, preferably, the electron beam apparatus comprises means forcorrecting astigmatism after exciting the objective lens using theexciting means with a voltage equal to the algebraic average with thepattern being charged, and then evaluating the pattern.

Also, the sixth embodiment provides an electron beam apparatus forconverging an electron beam using an electron-optical system includingan objective lens, and scanning a pattern with the electron beam toevaluate the pattern, characterized in that:

the objective lens comprises a first electrode applied with a voltageclose to a ground, and a second electrode applied with a voltage remotefrom the ground;

a focal distance of the objective lens can be changed by changing thevoltage applied to the first electrode; and

the exciting means comprises means for changing the voltage applied tothe second electrode to largely change the focal distance of theobjective lens, and means for changing the voltage applied to the firstelectrode to change the focal distance of the objective lens in a shorttime.

The sixth embodiment of the present invention also provides a devicemanufacturing method for evaluating a wafer in the middle of a processusing the electron beam apparatus.

A seventh embodiment of the present invention provides an electron beamapparatus for irradiating an object with an electron beam to perform atleast one of working, manufacturing, observation and testing of theobject, comprises:

a mechanical construction for determining a position of an electronicbeam with respect to the object, a piezoelectric element attached to themechanical construction for receiving a force from vibrations of themechanical construction; and a vibration attenuating circuitelectrically connected to the piezoelectric element to attenuateelectric energy output from the piezoelectric element.

When an object is irradiated with an electron beam to perform at leastone of working, manufacturing, observation and testing of the object, anexternal force including a vibration component at a resonant frequencyof proper vibration applied to a mechanical construction causes themechanical construction to amplify the vibration component at a resonantmagnification determined by its transfer function, and to vibrate. Thisvibration applies a force to the piezoelectric element. Thepiezoelectric element transduces the vibration energy of the mechanicalconstruction into electric energy which is output. However, since thevibration attenuating circuit attenuates this electric energy, thepiezoelectric element generates a force to cancel the external forceapplied to the piezoelectric element. In this way, the vibrationsgenerated by the mechanical resonance can be canceled to reduce theresonant magnification.

The mechanical construction is a portion or entirety of an electron beamapplied apparatus which generates problematic vibrations, and anarbitrary mechanical construction for aligning the electron beam. Forexample, the mechanical construction may be optics in an optical systemfor focusing an electron beam on an object, a barrel for containing suchan optical system, a supporting stand for carrying an object, or opticsin an optical system for focusing a secondary electron beam generated byirradiating the object with the electron beam on a detector, a barrelfor containing such an optical system, a barrel for containing thedetector, and so on.

The vibration attenuating circuit comprises at least inductive means asan element having an inductance or an equivalent circuit of the element,and the inductive means is connected to the piezoelectric element havinga static capacitance to form a resonant circuit. The inductance of theinductive means is determined with respect to the static capacitance ofthe piezoelectric element such that a resonant frequency of the resonantcircuit substantially matches a resonant frequency of the mechanicalconstruction.

Preferably, a resistive element is included in the vibration attenuatingcircuit. In this event, the capacitive impedance of the piezoelectricelement and the inductive impedance of the inductive means cancel eachother at the resonant frequency, so that the impedance of the resonantcircuit virtually has only a resistive element. Therefore, duringresonance, the electric energy output from the piezoelectric element issubstantially fully consumed by the resistive element.

The seventh embodiment of the present invention also provides asemiconductor manufacturing method which comprises a step of executingat least one of working and manufacturing of semiconductor devices, andobservation and testing of semiconductor devices during working orfinished ones, using the electron beam apparatus.

According to an eighth embodiment of the present invention, anelectrostatic chuck for electrostatically sucking and holding a wafer isapplied with a voltage which increases or decreases between zero volt toa predetermined voltage over time. The electrostatic chuck is comprisedof a laminate of a substrate, an electrode plate, and an insulatinglayer. A voltage associated with a voltage applied to a wafer is appliedto the electrode plate to generate an attractive force between the waferand the chuck. The electrode plate is divided into a first electrodecomprised of a central portion thereof and some of a peripheral portionthereof, and a second electrode comprised of the remaining portion. Thefirst electrode is first applied with a voltage, the wafer is thenplaced at a low potential or a ground potential, and subsequently thesecond electrode is applied with a voltage.

According to the eighth embodiment of the present invention, in acombination of a wafer and the electrostatic chuck for electrostaticallysucking and holding the wafer, the electrostatic chuck is formed of thelaminate of the substrate, electrode plate and insulating layer, thewafer is applied with a voltage through a predetermined resistor or acontact, and the contact is in the shape of a needle, the leading end ofwhich comes in contact with the back surface of the wafer, or in theshape of a knife edge, the edge of which comes in contact with the sidesurface of the wafer.

The eighth embodiment of the present invention also provides a devicemanufacturing method for sucking and holding a wafer using theelectrostatic chuck or the combination.

A ninth embodiment of the present invention provides an apparatus forcarrying a sample on an XY stage, moving the sample to an arbitraryposition in a vacuum, and irradiating the surface of the sample with anelectron beam, characterized in that:

the XY stage comprises a non-contact supporting mechanism by means ofstatic pressure bearings, and a vacuum sealing mechanism throughdifferential pumping;

a partition is disposed between a location of the sample which isirradiated with the beam and a static pressure bearing support of thestage for reducing a conductance; and

a pressure difference is produced between an electron beam irradiatingregion and the static pressure bearing support.

According to the ninth embodiment, the non-contact supporting mechanismby means of the static pressure bearings is applied to a supportingmechanism for the XY stage for carrying a sample thereon, and the vacuumsealing mechanism through differential exhaust is provided around thestatic pressure bearings such that a high pressure gas used for thestatic pressure bearing does not leak into a vacuum chamber, so that thestage device can demonstrate highly accurate positioning performance invacuum. Further, by forming the partition between the electron beamirradiated position and the static pressure bearing support for reducingthe conductance, even if a gas adsorbed on the surface of a sliding partof the stage is released each time the sliding part of the stage ismoved from a high pressure gas section to a vacuum environment, theexhausted gas hardly reaches the electron beam irradiated position,thereby preventing the pressure at the electron beam irradiated positionfrom rising. In other words, the employment of the foregoingconfiguration can stabilize the degree of vacuum at the electron beamirradiated position on the surface of the sample, and highly accuratelydrive the stage, thereby making it possible to accurately process thesample with the electron beam without contaminating the surface of thesample.

The partition may contain a differential exhaust structure. In thisevent, the partition is placed between the static pressure bearingsupport and the electron beam irradiating region, and a vacuumevacuation path is routed within the partition to provide a differentialpumping function, so that a gas released from the static pressurebearing support cannot pass through the partition into the electron beamirradiating region. In this way, the degree of vacuum at the electronbeam irradiated position can be further stabilized.

The partition may have a cold trap function. In this event, in a regionat a pressure of 10⁻⁷ Pa or higher, main components of a residual gas inthe vacuum and a gas released from the surface of the material are watermolecules. Therefore, if the water molecules can be efficientlyexhausted, a high degree of vacuum can be readily maintained withstability. Therefore, a cold trap cooled at approximately −100° C. to−200° C., if provided in the partition, enables the released gasgenerated on the static pressure bearing side to be frozen and trappedby the cold trap, so that the released gas pass into the electron beamirradiating region with difficulty, and the degree of vacuum is readilymaintained stable in the electron beam irradiating region. It goeswithout saying that the cold trap is effective not only for the watermolecules but also for removing organic gas molecules such as a oilgroup which is a factor of hampering a clean vacuum.

Further, the partitions may be disposed at two locations, i.e., near theelectron beam irradiated position and near the static pressure bearing.In this event, since the partitions which reduce the conductance aredisposed at two locations, i.e., near the electron beam irradiatedposition and near the static pressure bearing, the vacuum chamber isdivided into three chambers consisting of an electron beam irradiatingchamber, a static pressure bearing chamber, and an intermediate chamberthrough small conductance. Then, a vacuum evacuation system isconfigured to set lower pressures from the charged particle beamirradiation chamber to the intermediate chamber and to the staticpressure bearing chamber in this order. By doing so, even if thereleased gas causes a rise in pressure in the static pressure bearingchamber, a pressure fluctuating rate can be suppressed since this is achamber in which the pressure has been initially set high. Therefore,fluctuations in pressure to the intermediate chamber are suppressed bythe partition, thereby making it possible to reduce the fluctuations inpressure to a level at which substantially no problem arises.

The gas supplied to the static pressure bearings is preferably drynitrogen or inert gas. Also preferably, at least surfaces of partsfacing the static pressure bearings are applied with a surface treatmentfor reducing a released gas. As described above, on the sliding parts ofthe stage exposed to a high pressure gas atmosphere in the staticpressure bearing chamber, gas molecules included in the high pressuregas are adsorbed on their surfaces, and as the sliding parts are exposedto a vacuum environment, the adsorbed gas molecules are desorbed fromthe surfaces and act as a released gas which deteriorates the degree ofvacuum. It is therefore necessary, for preventing the deterioration ofthe degree of vacuum, to reduce the amount of gas molecules to beadsorbed, and promptly exhaust adsorbed gas molecules.

For this purpose, it is effective that the static pressure bearings aresupplied with a high pressure gas which is dry nitrogen, from whichmoisture has been sufficiently removed, or a highly pure inert gas (forexample, a highly pure nitrogen gas) to remove gas components which areadsorbed to a surface with ease and desorbed therefrom with difficulty(organic substances, moisture and so on) from the high pressure gas. Aninert gas such as nitrogen has a significantly low surface coverage to asurface and a significantly high desorbing speed from the surface, ascompared with moisture and organic substance. Therefore, when a highlypure inert gas, from which moisture and organic components have beenmaximally removed, is used for the high pressure gas, a small amount ofgas is released even when the sliding parts are moved from the staticpressure bearing chamber to the vacuum environment. Also, since thereleased gas promptly attenuates, the deterioration of the degree ofvacuum can be reduced. It is therefore possible to suppress a rise inpressure when the stage is moved.

Also effectively, at least surfaces of components, particularly,surfaces of parts which reciprocate between a high pressure gasatmosphere and a vacuum environment are applied with a surface treatmentfor reducing a released gas. As the surface treatment, when a basematerial is a metal, Tic (titanium carbide), TiN (titanium nitride),nickel plating, passivation, electrolytic polishing, compositeelectrolytic polishing, glass bead shot, and so on are contemplated.When a base material is Sic ceramics, coating of concise SiC layer byCVD and so on are contemplated. It is therefore possible to furthersuppress a rise in pressure when the stage is moved.

Also, the ninth embodiment of the present invention provides a waferdefect testing apparatus for testing the surface of a semiconductorwafer for defects using the electron beam apparatus. Since this canrealize the testing apparatus which is highly accurate in stagepositioning performance and stable in the degree of vacuum in theelectron beam irradiating region, a testing apparatus which has hightesting performance and is free from fear of contaminating the sample isprovided.

In addition, the ninth embodiment of the present invention also providesan exposure apparatus for drawing a circuit pattern of a semiconductordevice on the surface of a semiconductor wafer or a reticle using theelectron beam apparatus. Since this can realize the exposure apparatuswhich is highly accurate in stage positioning performance and stable inthe degree of vacuum in the electron beam irradiating region, anexposure apparatus which has high testing performance and is free fromfear of contaminating the sample is provided.

Furthermore, the ninth embodiment of the present invention also providesa semiconductor manufacturing method for manufacturing semiconductorsusing the electron beam apparatus. Since this results in manufacturingsemiconductors using the apparatus which is highly accurate in stagepositioning performance and stable in the degree of vacuum in theelectron beam irradiating region, fine semiconductor circuits can beformed.

A tenth embodiment of the present invention provides an apparatus forirradiating an electron beam to a sample carried on an XY stage,characterized in that:

the XY stage is contained in a housing and supported by static pressurebearings with respect to the housing in a non-contact manner;

the housing containing the stage is evacuated to vacuum; and

a differential exhaust mechanism is disposed around a portion of theelectron beam apparatus for irradiating an electron beam to the surfaceof the sample for evacuating a region on the surface of the sample inwhich the electron beam is irradiated.

In this way, a high pressure gas for the static pressure bearingsleaking into a vacuum chamber is first exhausted through a pipe forvacuum evacuation connected to the vacuum chamber. Then, by disposingthe differential exhaust mechanism around the portion in which anelectron beam is irradiated for evacuating a region in which theelectron beam is irradiated, the pressure in the electron beamirradiating region is made largely lower than the pressure in the vacuumchamber, thereby making it possible to stably achieve a degree of vacuumat which the sample can be processed with the electron beam withoutproblem. In other words, the sample on the stage can be stably processedwith the electron beam using the stage having a structure similar to astatic pressure bearing type stage which is generally used in theatmosphere (a stage supported by static pressure bearings, which doesnot have a differential exhaust mechanism).

The gas supplied to the static pressure bearings of the XY stage ispreferably dry nitrogen or a highly pure inert gas. The highly pureinert gas is preferably pressurized after exhausted from the housingwhich contains the stage, and again supplied to the static pressurebearings. In this way, the remaining gas component in the vacuum housingis a highly pure inert gas, so that the surface of the constructionwithin the vacuum chamber is not susceptible to contamination bymoisture, oil component and so on. In addition, even if inert gasmolecules are adsorbed on the surface of the sample, they are promptlydesorbed from the surface of the sample if they are exposed to thedifferential exhaust mechanism or a high vacuum in the electron beamirradiating region, thereby making it possible to minimize the influenceon the degree of vacuum in the electron beam irradiating region andstabilize the processing on the sample with the electron beam.

The tenth embodiment of the present invention provides a wafer defecttesting apparatus for testing the surface of a semiconductor wafer fordefects using the electron beam apparatus. It is therefore possible toprovide a testing apparatus, at a low cost, which is highly accurate instage positioning performance and stable in the degree of vacuum in theelectron beam irradiating region.

The tenth embodiment of the present invention provides an exposureapparatus for drawing a circuit pattern of a semiconductor device on thesurface of a semiconductor wafer or a reticle using the electron beamapparatus. It is therefore possible to provide an exposure apparatus, ata low cost, which is highly accurate in stage positioning performanceand stable in the degree of vacuum in the electron beam irradiatingregion.

The tenth embodiment of the present invention provides a semiconductormanufacturing method for manufacturing semiconductors using the electronbeam apparatus. Since this results in manufacturing semiconductors usingthe apparatus which is highly accurate in stage positioning performanceand stable in the degree of vacuum in the electron beam irradiatingregion, fine semiconductor circuits can be formed.

An eleventh embodiment of the present invention provides an electronbeam apparatus which comprises a plurality of optical systems each forgenerating a primary electron beam, converging the primary electronbeam, scanning the primary electron beam on a sample for irradiation,and detecting a secondary electron beam emitted from an electron beamirradiated portion of the sample using a detector, characterized bycomprising a retarding voltage applying unit for applying the samplewith a retarding voltage, and a function for applying an optimalretarding voltage depending on the sample, wherein the optical systemcomprises at least one axially symmetric lens produced by working a bulkof insulating material, and having the surface applied with a metalcoating.

The eleventh embodiment of the present invention also provides anelectron beam apparatus which has a primary optical system forgenerating a primary electron beam, converging the primary electronbeam, and scanning the primary electron beam on a sample forirradiation, wherein a secondary electron beam emitted from an electronbeam irradiated portion of the sample is accelerated, separated from theprimary optical system by an ExB separator, and detected by a detector,characterized by comprising a retarding voltage applying unit forapplying the sample with a retarding voltage, a charge-up checkingfunction unit for checking a charge-up state of the sample, and afunction for determining an optimal retarding voltage based oninformation output from the charge-up checking function unit to applythe retarding voltage to the sample or to change it to an optimal beamcurrent.

The eleventh embodiment of the present invention also provides anelectron beam apparatus which is characterized by having an opticalsystem for irradiating an electron beam to a sample, and a charge-upchecking function, wherein the charge-up checking function evaluates adistorted pattern or a blurred pattern at a particular site of thesample, when the secondary electron beam generated from the sampleirradiated with the primary electron beam is detected to form an image,and evaluates that charge-up is large when the result shows that thedistorted pattern or the blurred pattern is large.

The charge-up checking function can apply the sample with a variableretarding voltage, and forms an image near a boundary where a patterndensity largely varies on the sample which is applied with at least tworetarding voltages, and may have a device for displaying the image suchthat an operator can evaluate the distorted pattern or the blurredpattern.

Also, the eleventh embodiment of the present invention provides a devicemanufacturing method characterized by detecting defects on a wafer inthe middle of a process using the electron beam apparatus.

A twelfth embodiment of the present invention provides a defect testingapparatus for testing a sample for defects, characterized by comprising:

image capturing means for capturing each of images of a plurality ofregions under testing displaced from one another while partiallyoverlapping on the object under testing on the sample;

means for storing a reference image; and

defect determining means for comparing the images of the plurality ofregions under testing captured by the image capturing means with thereference image stored in the storage means to determine defects on thesample. Here, while the sample under testing may be selected fromarbitrary ones for which defects can be detected, the present inventioncan produce a distinct effect when a semiconductor wafer is intended.

In this embodiment, the image capturing means operates to capture eachof the images of the plurality of regions under testing displaced fromone another while partially overlapping on the object under testing onthe sample, and the defect determining means operates to compare theimages of the plurality of regions under testing captured by the imagecapturing means with the reference image stored in the storage means todetermine defects on the sample.

In this way, since the twelfth embodiment of the present invention cancapture a plurality of images of regions under testing at differentpositions, an image under testing with less discrepancy in position withthe reference image can be selectively utilized in a subsequent process,thereby making it possible to prevent a degraded defect detectingaccuracy due to misalignment. Moreover, even if the sample and the imagecapturing means is in such a positional relationship that a portion of apattern under testing is normally lost from the image region undertesting, it is highly likely that the entire pattern under testing liesin any of regions covered by the plurality of images of the regionsunder testing displaced from one another, thereby making it possible toprevent erroneous detection of defect due to such partial loss of thepattern.

The comparing means performs a so-called matching operation between eachof the captured images of the plurality of regions under testing and thereference image, and operates to determine that the sample isnon-defective if there is substantially no difference between at leastone image of the plurality of regions under testing and the referenceimage. Conversely, if there is a substantial difference between all theimages of the regions under testing and the reference image, the sampleis determined as defective, thereby detecting defects at a higheraccuracy.

In the twelfth embodiment, electron irradiating means is furtherprovided for irradiating a primary electron beam to each of a pluralityof regions under testing to emit secondary electron beams from thesample, wherein the image capturing means detects the secondary electronbeams emitted from the plurality of regions under testing, therebymaking it possible to sequentially capture the images of the pluralityof regions under testing.

Further, the electron irradiating means preferably comprises a particlebeam source for emitting primary electrons, and deflecting means fordeflecting the primary electrons, such that a primary electron beamemitted from the particle beam source is deflected by the deflectingmeans to sequentially irradiate the primary electron beam to theplurality of regions under testing. In this event, since the position ofan input image can be readily changed by the deflecting means, aplurality of images under testing at different positions can be capturedat a high speed.

The twelfth embodiment of the present invention also provides asemiconductor device manufacturing method which includes a step oftesting a wafer during working or a finished one for defects, using theelectron beam apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram generally illustrating the configuration of atesting apparatus which is a first embodiment of a charged particle beamapparatus according to the present invention;

FIG. 2( a) is a plan view of an electron deflection system, and FIG. 2(b) is a cross-sectional view of the same;

FIG. 3 is a flow chart illustrating an embodiment of a semiconductordevice manufacturing method according to the present invention;

FIG. 4( a) is a flow chart illustrating a lithography step which formsthe core of wafer processing steps in FIG. 3, and FIG. 4( b) is a flowchart illustrating a wafer testing step in the wafer processing steps inFIG. 3;

FIG. 5 is an elevation illustrating the main components of a testingapparatus which is a second embodiment of the charged particle beamapparatus according to the present invention, viewed along a line A-A inFIG. 6;

FIG. 6( a) is a plan view of the main components of the testingapparatus illustrated in FIG. 5, viewed along a line B-B in FIG. 5, andFIG. 6( b) is a diagram illustrating an exemplary modification to theconfiguration illustrated in FIG. 6( a);

FIG. 7 is a cross-sectional view illustrating an mini-environment devicein FIG. 5, viewed along a line C-C;

FIG. 8 is a diagram illustrating a loader housing in FIG. 5, viewedalong a line D-D in FIG. 6( a);

FIGS. 9[A] and 9[B] are an enlarged view of a wafer rack, wherein FIG.9[A] is a side view and FIG. 9[B] is a cross-sectional view taken alonga line E-E in FIG. 9[A];

FIGS. 10[A] and 10[B] are diagrams illustrating exemplary modificationsto a method of supporting a main housing;

FIG. 11 is a schematic diagram illustrating a general configuration ofan electron-optical device in the testing apparatus of FIG. 5;

FIG. 12 is a diagram illustrating a potential applying mechanism;

FIGS. 13[A] and 13[B] show diagrams for explaining an electron beamcalibration mechanism, where FIG. 13[A] is a side view and FIG. 13[B] isa plan view;

FIG. 14 is a schematic explanatory view of a wafer alignment controller;

FIG. 15 is a cross-sectional view generally illustrating a thirdembodiment of the charged electron beam apparatus according to thepresent invention;

FIG. 16 is a configuration diagram schematically illustrating anevaluation apparatus which is a fourth embodiment of the chargedelectron beam apparatus according to the present invention;

FIG. 17 is a table showing a breakdown occurrence probability for eachmetal;

FIG. 18 is a perspective view and a cross-sectional view of anelectrode;

FIG. 19 is a partial cross-sectional view of the electrode illustratedin FIG. 18;

FIG. 20 is a top plan view and a cross-sectional view of the electrodeillustrated in FIG. 18;

FIG. 21 is an enlarged cross-sectional view of a main portion of theelectrode illustrated in FIG. 20;

FIG. 22 is a diagram generally illustrating a fifth embodiment of thecharged particle beam apparatus according to the present invention;

FIG. 23 is a diagram illustrating in detail the configuration of theelectron beam apparatus illustrated in FIG. 22;

FIG. 24 is a diagram generally illustrating a sixth embodiment of thecharged particle beam apparatus according to the present invention;

FIG. 25( a) is a graph showing the relationship between a negativevoltage applied to an objective lens and a rising width of an electricsignal, and FIG. 25( b) is a diagram for explaining the rising width ofthe electric signal;

FIG. 26 is a configuration diagram of an electron beam testing apparatuswhich is a seventh embodiment of the charged particle beam apparatusaccording to the present invention;

FIGS. 27 (a) to 27(c) are diagrams generally illustrating blocks in amechanical construction of the electron beam testing apparatusillustrated in FIG. 26, where FIG. 27( a) shows the relationship betweenthe electron beam testing apparatus and coordinate axes; FIG. 27( b)shows the proper vibration of a barrel; and FIG. 27( c) shows anactuator attached to cancel the proper vibrations;

FIG. 28 is a schematic diagram illustrating an actuator and a vibrationattenuating circuit used in the electron beam testing apparatusillustrated in FIG. 26, as well as the configuration of an equivalentcircuit of a formed series resonant circuit;

FIG. 29 is a graph showing a transfer function of the barrel in theelectron beam testing apparatus illustrated in FIG. 26;

FIG. 30 is a graph showing the transfer function of the barrel, electricfrequency characteristic of the series resonant circuit, and a totaltransfer function in the electron beam testing apparatus illustrated inFIG. 26;

FIGS. 31( a) to 31(c) are diagrams for explaining a wafer testing methodaccording to the present invention, where FIG. 37( a) shows patterndefect detection; FIG. 37( b) line width measurement; and FIG. 37( c)potential contrast measurement, respectively;

FIG. 32 is a schematic plan view of an electrostatic chuck in an eighthembodiment of the electron beam apparatus according to the presentinvention, i.e., a plan view with a wafer removed to show electrodes;

FIG. 33 is a schematic vertical cross-sectional view taken along astraight line M-M in FIG. 32, a cross-sectional view showing a state inwhich a wafer is carried but not applied with a voltage;

FIGS. 34( a) and 34(b) are time charts of voltages applied to electrodesand a wafer;

FIG. 35 is a block diagram illustrating an exemplary configuration of anelectron beam apparatus which uses the electrostatic chuck illustratedin FIG. 32;

FIGS. 36[A] and 36[B] are diagrams illustrating a vacuum chamber and anXY stage of a conventional electron beam apparatus, where FIG. 36[A] isa front view and FIG. 36[B] is a side view;

FIG. 37 is a diagram for explaining a differential pumping mechanism inFIG. 36;

FIGS. 38[A] and 38[B] are diagrams illustrating a vacuum chamber and anXY stage in a ninth embodiment of the charged particle beam apparatusaccording to the present invention, where FIG. 38[A] is a front view andFIG. 38[B] is a side view;

FIG. 39 is a diagram illustrating a vacuum chamber and an XY stage in afirst exemplary modification to the ninth embodiment of the presentinvention;

FIG. 40 is a diagram illustrating a vacuum chamber and an XY stage in asecond exemplary modification to the ninth embodiment of the presentinvention;

FIG. 41 is a diagram illustrating a vacuum chamber and an XY stage in athird exemplary modification to the ninth embodiment of the presentinvention;

FIG. 42 is a diagram illustrating a vacuum chamber and an XY stage in afourth exemplary modification to the ninth embodiment of the presentinvention;

FIG. 43 is a schematic diagram showing an example of an optical systemand a detection system disposed in a barrel illustrated in FIGS. 38-42;

FIG. 44 is a diagram illustrating a vacuum chamber and an XY stage in atenth embodiment of the charged particle beam apparatus according to thepresent invention;

FIG. 45 is a diagram illustrating an example of a differential pumpingmechanism disposed in the apparatus illustrated in FIG. 44;

FIG. 46 is a diagram illustrating a gas circulation piping systeminstalled in the apparatus illustrated in FIG. 44;

FIG. 47 is a schematic diagram of an optical system in an eleventhembodiment of the charged electron beam apparatus according to thepresent invention;

FIG. 48 is a diagram illustrating a state of arrayed barrels of theelectron beam apparatus illustrated in FIG. 47;

FIG. 49 is a diagram for explaining a site at which charge-up isevaluated, and an evaluation method;

FIG. 50 is a schematic configuration diagram of a defect testingapparatus which is a twelfth embodiment of the charged particle beamapparatus according to the present invention;

FIG. 51 is a diagram illustrating examples of a plurality of imagesunder testing captured by the defect testing apparatus of FIG. 50 and areference image;

FIG. 52 is a flow chart illustrating the flow of a main routine of wafertesting in the defect testing apparatus of FIG. 50;

FIG. 53 is a flow chart illustrating in detail the flow of a subroutinefor a step of acquiring data on a plurality of images under testing(step 1904) in FIG. 52;

FIG. 54 is a flow chart illustrating in detail the flow of a subroutinefor a comparing step (step 1908) in FIG. 52;

FIG. 55 is a diagram illustrating a specific example of theconfiguration of a detector in the defect testing apparatus in FIG. 50;and

FIG. 56 is a diagram conceptually illustrating a plurality of regionsunder testing which are shifted in position from one another whilepartially overlapping with one another on the surface of a semiconductorwafer.

BEST MODE FOR IMPLEMENTING THE INVENTION

In the following, a variety of embodiments of a charged particles beamapparatus according to the present invention will be described for anelectron beam based apparatus which is taken as an example. Anyembodiment is suitable for use in a sheet beam based testing apparatus.

Embodiment Relating to Overall Structure of Apparatus First Embodiment

A first embodiment of the charged particle beam apparatus according tothe present invention relates to an electron beam based projectionsystem, so that the projection system will be described first.

The projection system involves collectively irradiating a region underobservation on a sample with a primary electron beam, i.e., irradiatinga fixed area without scanning, and focusing a secondary electron beamfrom the irradiated region collectively on a detector (a combination ofa micro-channel plate and a fluorescent plate) through a lens system asan image of the secondary electron beam. This image is transduced intoan electric signal by a two-dimensional CCD (solid-state imager device)or TDI-CCD (line image sensor) to output on a CRT or to store in astorage device. From this image information, defects on the sample wafer(a semiconductor (Si) wafer in the middle of a process) are detected.With a CCD, a stage is moved in the minor axis direction or major axisdirection, and movements are made on a step-and-repeat basis. WithTDI-CCD, the stage is continuously moved in an integrating direction.Since the TDI-CCD can sequentially capture images, the TDI-CCD is usedwhen a defect testing is conducted continuously. The resolution isdetermined by a scaling factor, accuracy and so on of a focusing opticalsystem (secondary optical system), and the resolution of 0.05 μm hasbeen achieved, by way of example. In this event, with the resolution of0.1 μm, when 1.6 μA is applied to an area of 200 μm×50 μm as an electronbeam irradiating condition, approximately one hour of testing time isrequired for every 20 cm wafer, which is faster than the SEM system by afactor of eight. The specifications of the TDI-CCD used herein define2048 pixels×512 stages, and a line rate at 3.3 microseconds (linefrequency at 300 kHz). While the irradiated area in this example isfitted to the specifications of the TDI-CCD, the irradiated area may bechanged depending on an object under irradiation.

Now, the relationship between main functions of the map projectionsystem, and its general figure will be described with reference toFIG. 1. In FIG. 1, the testing apparatus has a primary column 2001, asecondary column 2002, and a chamber 2003. In the primary column 2001,an electronic gun 2004 is arranged, and a primary optical system 2005 ispositioned on the optical axis of an electron beam (primary electronbeam) emitted from the electron gun 2004. In the chamber 2003, in turn,a stage 2006 is arranged, and a sample 2007 is carried on the stage2006.

On the other hand, in the secondary column 2002, a cathode lens 2008, anumerical aperture (NA) 2009, a Wien filter (ExB filter) 2010, a secondlens 2011, a field aperture 2012, a third lens 2013, a fourth lens 2014,and a detector 2015 are positioned on the optical axis of a secondaryelectron beam generated from the sample 2007. The numerical aperture2009, which corresponds to a diagram, is made of a thin plate of metal(Mo or the like) formed with a circular hole extending therethrough, andis positioned such that its opening is at a convergence position of theprimary electron beam as well as a focus position of the cathode lens2008. Therefore, the cathode lens 2008 and the numerical aperture 2009constitute a telecentric electron-optical system.

The output of the detector 2015 is input to a control unit 2016, whilethe output of the control unit 2016 is input to a CPU 2017. A controlsignal of the CPU 2017 is input to a primary column control unit 2018, asecondary column control unit 2019, and a stage driving mechanism 2020.The primary column control unit 2018 controls a lens voltage for theprimary optical system 2005, while the secondary column control unit2019 controls lens voltages for the cathode lens 2008 and second lens2011—fourth lens 2014, as well as controls an electromagnetic fieldapplied to the Wien filter 2010.

The stage driving mechanism 2020 transfers stage position information tothe CPU 2017. Also, the primary column 2001, secondary column 2002 andchamber 2003 are connected to a vacuum exhaust system (not shown), suchthat they are evacuated by a turbo molecular pump in the vacuum exhaustsystem to maintain a vacuum state therein.

A primary electron beam emitted from the electron gun 2004 impinges onthe Wien filter 2010 while receiving a lens action by the primaryoptical system 2005. As a chip for the electron gun, L_(a)B₆, capable ofdrawing a large current with a rectangular cathode, is preferably used.

The primary optical system 2005 uses quadrupole or octpole electrostatic(or electromagnetic) lenses which are asymmetric about the optical axis.This can give rise to convergence and divergence on each of the X-axisand Y-axis, similarly to a so-called cylindrical lens. The lenses areconfigured in two stages or in three stages to optimize conditions forthe respective lenses, thereby making it possible to shape an electronbeam irradiated region on the surface of a sample into an arbitraryrectangle or ellipse without losing the irradiated electron beam.Specifically, when electrostatic lenses are used, four cylindrical rodsare used to place opposing electrodes (a and b, c and d) at an equalpotential and impart them opposite voltage characteristics. Instead ofcylindrical ones, a lens having a shape resulting from dividing acircular plate generally used in an electrostatic deflector into fourmay be used as the quadrupole lens. In this event, the lenses can bereduced in size.

The primary electron beam passing through the primary optical system2005 has its trajectory deflected by a deflecting action of the Wienfilter 2010. As described later, the Wien filter 2010 can generate amagnetic field and an electric field orthogonal to each other. Assumingnow that an electric field is E, a magnetic field is B, and the velocityof electrons is v, the Wien filter allows only electrons which satisfythe Wien condition E=vB to go straight, and deflects the trajectories ofthe remaining electrons. For the primary electron beam, a force FB isgenerated from the magnetic field and a force FE is generated from theelectric field to deflect the beam trajectory. On the other hand, forthe secondary electron beam, since the forces FB and FE act in theopposite directions, they cancel each other, allowing the secondaryelectron beam to go straight therethrough as it is.

A lens voltage for the primary optical system 2005 has been previouslyset such that the primary electron beam is focused on the opening of thenumerical aperture 2009. The numerical aperture 2009 acts to preventexcessive electron beams dispersed within the apparatus from reachingthe surface of the sample, and to prevent the sample 2007 from chargingand contamination. Further, since the numerical aperture 2009 and thecathode lens 2008 constitute a telecentric electron-optical system, theprimary electron beam transmitting the cathode lens 2008 is transformedinto a parallel beam which is uniformly and evenly irradiated to thesample 2007. In other words, Koehler illumination, so called in theoptical microscope, is implemented.

As the sample 2007 is irradiated with the primary electron beam,secondary electrons, reflected electrons or back-scattered electrons areemitted from the beam irradiated surface of the sample 2007 as asecondary electron beam. The secondary electron beam transmits thecathode lens 2008 while receiving a lens action thereof. The cathodelens 2008 comprises three electrodes. The lowermost electrode isdesigned to form a positive electric field between itself and apotential close to the sample 2007 to draw electrons (particularly, lessdirectional secondary electrons) and efficiently introduce the electronsinto the lens. The lens action is generated by applying voltages to thefirst and second electrodes of the cathode lens 2008, and placing thethird electrode at a zero potential.

On the other hand, the numerical aperture 2009 is placed at a focusposition of the cathode lens 2008, i.e., a back focus position from thesample 2007. Therefore, light flux of an electron beam emitted out ofthe center of the view field (out of axis) is transformed into aparallel beam which passes through the central position of the numericalaperture 2009 without eclipse. The numerical aperture 2009 serves toreduce lens aberration of the second lens 2011—fourth lens 2014 for thesecondary electron beam.

The secondary electron beam passing through the numerical aperture 2009goes straight as it is without receiving a deflecting action of the Wienfilter 2010. By changing the electromagnetic field applied to the Wienfilter 2010, electrons having particular energy (for example, secondaryelectrons, reflected electrons or back-scattered electrons) alone can beintroduced into the detector 2015 from the secondary electron beam.

If the secondary electron beam is focused only with the cathode lens2008, aberration is more likely to occur due to a stronger lens action.Therefore, image formation is performed once in combination of thesecond lens 2011. The secondary electron beam provides intermediateimage formation on the field aperture 2012 by the cathode lens 2008 andsecond lens 2011. In this event, generally, the magnification requiredas the secondary optical system is often insufficient, so that the thirdlens 2013 and forth lens 2014 are added to the configuration as lensesfor enlarging the intermediate image. The secondary electron beam isenlarged by the third lens 2013, fourth lens 2014 and forms an image.Here, the secondary electron beam forms images a total of three times.Alternatively, the third lens 2013 and fourth lens 2014 may be combinedto force the secondary electron beam to form an image once (a total oftwo times).

All of the second lens 2011, third lens 2013 and fourth lens 2014 arelenses symmetric about the optical axis, which are called uni-potentiallenses or Einzel lenses. Each of the lenses comprises three electrodes,where the two outer electrodes are generally placed at zero potential,and a voltage applied to the central electrode generates a lens actionfor controlling. Also, the field aperture 2012 is positioned at anintermediate image formation point. While the field aperture 2012 limitsthe field of view to a required range, similar to a viewing diaphragm ofan optical microscope, it blocks excessive beams together with the thirdlens 2013 and fourth lens 2014, for electronic beams, to prevent thedetector 2015 from charging and contamination. The magnification is setby changing lens conditions (focal lengths) of the third lens 2013 andfourth lens 2014.

The secondary electron beam is enlarged and projected by the secondaryoptical system, and is focused on a detecting face of the detector 2015.The detector 2015 is comprised of a micro-channel plate (MCP) foramplifying electrons; a fluorescent plate for transducing electrons intolight; a lens and other optics for relaying a vacuum system to theoutside to transmit an optical image; and an imager device (CCD or thelike). The secondary electron beam is focused on the MCP detecting face,amplified, transduced into an optical signal by the fluorescent plate,and opto-electrically transduced into an electric signal by the imagerdevice.

The control unit 2016 reads an image signal of the sample from thedetector 2015 for transmission to the CPU 2017. The CPU 2017 conducts apattern defect testing from the image signal through template matchingor the like. The stage 2006 is movable in the XY directions by the stagedriving mechanism 2020. The CPU 2017 reads the position of the stage2006, outputs a driving control signal to the stage driving mechanisms2020 to drive the stage 2006, and sequentially detects an image andconducts the testing.

In this way, in the testing apparatus in the first embodiment, thenumerical aperture 2009 and the cathode lens 2008 constitute atelecentric electron-optical system, so that the sample can be uniformlyirradiated with the primary electron beam. In other words, the Koehlerillumination can be readily implemented. Further, for the secondaryelectron beam, an overall primary beam from the sample 2007 impingesperpendicularly on the cathode lens 2008 (parallel with the optical axisof the lens) and passes through the numerical aperture 2009, so thatperipheral light will not eclipsed or the luminance of an image will notbe degraded in a peripheral portion of the sample. In addition, althoughso-called magnification chromatism, i.e., difference in the position ofimage formation due to variations in energy possessed by electrons,occurs (particularly, large magnification chromatism occurs since thesecondary electron beam has largely varying energy), the numericalaperture 2009 is placed at the focus position of the cathode lens 2008,so that this magnification chromatism can be suppressed.

Since the magnification is changed after the passage through thenumerical aperture 2009, a uniform image can be generated over theentire field of view on the detection side, even if set magnificationsare changed in the lens conditions for the third lens 2013 and fourthlens 2014.

While an even and uniform image can be captured in this embodiment,generally, as the magnification is increased, a problem arises that thebrightness of image is reduced. To improve this, the lens conditions forthe primary optical system may be designed such that when themagnification is changed by modifying the lens conditions for thesecondary optical system, an effective field of view on the surface of asample determined thereby is identical in size to an electron beamirradiated onto the surface of the sample. Specifically, while the fieldof view becomes narrower as the magnification is larger, the irradiatedenergy density of the electron beam is increased simultaneously withthis, so that a signal density of detected electrons is held constant atall times to avoid the reduced brightness of image even if the field ofview is enlarged and projected in the secondary optical system.

Also, in the testing apparatus of the first embodiment, the Wien filter2010 is used to deflect the trajectory of the primary electron beam andallow the secondary electron beam to go straight therethrough, thepresent invention is not limited to that, but a Wien filter may be usedfor allowing the primary electron beam to go straight therethrough whiledeflecting the trajectory of the secondary electron beam. Further, whilea rectangular beam is formed from a rectangular cathode and a quadrupolelens in this embodiment, the present invention is not limited to this.For example, a rectangular beam or an elliptic beam may be created froma circular beam, or a circular beam may be passed through a slit toextract a rectangular beam. Also, a plurality of beams may be scannedsuch that electron beams are generally irradiated uniformly to anirradiated region. The scanning in this event may be performed such thatthe plurality of beams arbitrarily scan respective regions allocatedthereto (however with a uniform amount of irradiation).

Explaining now the electron gun as an electron beam source, a thermalelectron beam source may be used as the electron beam source in thisembodiment. An electron emitter (cathode) is made of L_(a)B₆. However,another material may be used as long as it is refractory (the vaporpressure is low at high temperatures) and small in work function.Preferably, the tip is formed in the shape of cone or truncated coneresulting from cutting off the tip of a cone. The tip of the truncatedcone may have a diameter of approximately 100 μm. While an fieldemission type or thermal field emission type electron beam source may beused as another system, an L_(a)B₆ based thermal electron source isoptimal for this embodiment in which a relatively wide region (forexample, 100×25−400×100 μm²) is irradiated with a large current(approximately 1 μA). (In the SEM system, a thermal electric fieldelectron beam source is generally used).

The thermal electron beam source is based on a method of emittingelectrons by heating an electron emitting material, while the thermalfield emission electron beam source means a method for emittingelectrons by applying the electron emitting material with a highelectric field, and stabilizing the emission of electrons by heating theelectron beam emitter.

As will be understood from the description with reference to FIG. 1, thefunctions of main components in the projection system are as follows.First, as to the primary electron-optical system, a section for formingelectron radiations emitted from an electron gun into a beam shape andirradiating a wafer surface with a rectangular or circular (elliptic)electron beam is called the “primary electron-optical system.” The sizeand current density of the electron beam can be controlled bycontrolling the lens conditions for the primary electron-optical system.Also, the primary electron beam is directed perpendicular to the waferby a Wien filter positioned at a junction of the primary/secondaryelectron-optical systems.

Thermal electrons emitted from an L_(a)B₆ cathode of the electron gun isfocused as a cross-over image on a gun diaphragm by a Wehnelt, tripleanode lens. An electron beam with an incident angle adapted to the lenswith an illumination field diagram is focused on a numerical aperturediagram in the form of rotational asymmetry by controlling the primaryelectrostatic lens, and subsequently two-dimensionally irradiated onto awafer surface. A rear stage of the primary electrostatic lens iscomprised of a three-stage quadrupole (QL) and a one-stage electrode forcorrecting geometrical aberration. While the quadrupole lens haslimitations such as strict alignment accuracy, it characteristically hasa strong converging action as compared with a rotationally symmetricallens, so that it can correct the geometrical aberration corresponding tospherical aberration of a rotationally symmetric lens by applying anappropriate voltage to the geometrical aberration correcting electrode.In this way, a uniform surface beam can be irradiated to a predeterminedregion.

Next, as to the secondary electron-optical system, a focusing/projectionoptical system for focusing a two-dimensional secondary electron imageproduced by processing a secondary electron beam generated from a waferirradiated with a primary electron beam at the position of a fielddiaphragm by electrostatic lenses (CL, TL) corresponding to an objectivelens, and enlarging and projecting the secondary electron image using alens (PL) at a rear stage, is called the “secondary electron-opticalsystem.” In this event, the wafer is applied with a minus bias voltage(decelerating electric field voltage). A decelerating electric field hasa decelerating effect for an irradiated beam, and also has effects ofreducing a damage on a wafer (sample), accelerating the secondaryelectron beam generated from the surface of the sample due to apotential difference between CL and the wafer, and reducing chromatism.Electrons converged by CL is focused on FA by TL, and the resultingimage is enlarged and projected by PL, and formed on a secondaryelectron beam detector (MCP). In the secondary electron-optical system,NA is positioned between CL-TL and optimized to constitute an opticalsystem which is capable of reducing off-axis aberration.

In addition, for correcting errors caused by the manufacturing of theelectron-optical system, and astigmatism and anisotropic magnificationof an image produced by passing a Wien filter, an electrostatic octpole(STIG) is disposed for correction, and preferably, a deflector (OP)positioned between respective lenses may be used to correctmisalignment. In this way, a projection optical system can be achievedwith a uniform resolution in the field of view.

The Wien filter 2010 is a unit based on an electromagnetic prism opticalsystem which has electrodes and magnetic poles positioned in orthogonaldirections to generate an electric field and a magnetic field in anorthogonal relationship. As an electromagnetic field is selectivelyapplied, an electron beam incident from one direction into the field isdeflected, while an electron beam incident from the opposite directionis allowed to go straight. This is achieved because of the ability tocreate conditions (Wien conditions) for canceling a force received byelectrons from the electric field and a force received thereby from themagnetic field, whereby the primary electron beam is deflected andirradiated perpendicularly onto a wafer, while the secondary electronbeam goes straight toward the detector.

The detailed structure of the Wien filter 2010 as an electron beamdeflector will be described with reference to FIGS. 2( a) and 2(b). Asillustrated in these figures, a field generated by the electron beamdeflector has a structure in which an electric field is orientedorthogonal to a magnetic field in a plane perpendicular to the opticalaxis of the aforementioned projection optical system, i.e., an ExBstructure.

Here, the electric field is generated by electrodes 2030 a, 2030 b whichhave concave curved surfaces. The electric fields generated by theelectrodes 2030 a, 2030 b are controlled by controllers 2031 a, 2031 b,respectively. Electromagnetic coils 2032 a, 2032 b are arrangedorthogonal to the electrodes 2030 a, 2030 b for generating the magneticfield. In this event, for improving the uniformity of the magneticfield, a pole piece having a parallel flat plate shape is provided toform a magnetic path. While the electrodes 2030 a, 2030 b for generatingthe electric field may be arranged symmetric about a point 2034, theymay be concentrically arranged.

FIG. 2( b) is a vertical cross-sectional view on a plane which passesthe point 2034 in FIG. 2( a) and perpendicular to the electrodes 2030 a,2030 b. Referring to FIG. 2( b), behaviors of electron beams will bedescribed. Irradiated electron beams 2035 a, 2035 b are deflected by anelectric field generated by the electrodes 2030 a, 2030 b and a magneticfield generated by the electromagnetic coils 2031 a, 2031 b, and thenimpinge on the surface of a sample in a direction perpendicular thereto.Here, incident positions and angles of the irradiated electron beams2035 a, 2035 b to the Wien filter 2010 are uniquely determined as theenergy of electrons is determined. Further, by controlling conditions ofthe electric field and magnetic field, i.e., the electric fieldgenerated by the electrodes 2030 a, 2030 b and the magnetic fieldgenerated by the electromagnetic coils 2031 a, 2031 b by theirrespective controllers 2031 a, 2031 b, 2033 a, 2033 b such that thesecondary electron beams 2036 a, 2036 b go straight, i.e., vB=E stands,secondary electron beams go straight through the Wien filter 2010 andimpinges on the projection optical system, where v is the velocity ofelectrons (m/s), B is the magnetic field (T), e is the amount of charge(C), and E is the electric field (V/m).

Finally, the detector will be described. The image of the secondaryelectron beam from the wafer, focused by the secondary optical system isfirst amplified by the micro-channel plate (MCP), then strikes thefluorescent screen, and transduced into a light image. The MCP iscomprised of several millions of very thin conductive glass capillariesof 6-25 μm in diameter and 0.24-1.0 mm in length which are bundled andshaped into a thin plate. Each of the capillaries acts as an independentsecondary electron amplifier, when a predetermined voltage is applied,to form, as a whole, the secondary electron amplifier. An imagetransduced into light by this detector is projected through a vacuumtransmission window onto TDI-CCD on a one-to-one basis in an FOP systemwhich is placed in the atmosphere.

As will be understood from the foregoing description, the testingapparatus, which is the first embodiment, can improve the throughput ofthe electron beam based testing apparatus.

FIG. 3 illustrates an example of a semiconductor device manufacturingmethod which uses the first embodiment of the present invention, andincludes the following main processes.

(1) a wafer manufacturing process for manufacturing a wafer (or a waferpreparing process for preparing a wafer);

(2) a mask manufacturing process for manufacturing masks for use inexposure (or mask preparing process for preparing masks);

(3) a wafer processing process for performing processing required to thewafer;

(4) a chip assembling process for excising one by one chips formed onthe wafer and making them operable; and

(5) a chip testing process for testing complete chips.

The respective main processes are further comprised of severalsub-processes.

Among these main processes, the wafer processing process set forth in(3) exerts critical affections to the performance of resultingsemiconductor devices. This process involves sequentially laminatingdesigned circuit patterns on the wafer to form a large number of chipswhich operate as memories, MPUs and so on. The wafer processing processincludes the following sub-processes:

(A) a thin film forming sub-process for forming dielectric thin filmsserving as insulating layers, metal thin films for forming wirings orelectrodes, and so on (using CVD, sputtering and so on);

(B) an oxidization sub-process for oxidizing the thin film layers andthe wafer substrate;

(C) a lithography sub-process for forming a resist pattern using masks(reticles) for selectively processing the thin film layers and the wafersubstrate;

(D) an etching sub-process for processing the thin film layers and thesubstrate in conformity to the resist pattern (using, for example, dryetching techniques);

(E) an ion/impurity injection/diffusion sub-process;

(F) a resist striping sub-process; and

(G) a sub-process for testing the processed wafer.

The wafer processing process is repeated a number of times equal to thenumber of required layers to manufacture semiconductor devices whichoperate as designed.

FIG. 4( a) is a flow chart illustrating the lithography process (C)which forms the core of the wafer processing process in FIG. 3. Thelithography process includes the following steps:

(a) a resist coating step for coating a resist on the wafer on whichcircuit patterns have been formed in the previous process;

(b) a step of exposing the resist;

(c) a developing step for developing the exposed resist to produce aresist pattern; and

(d) an annealing step for stabilizing the developed resist pattern.

When the defect testing apparatus of the present invention is used inthe testing sub-process set forth in (G), any semiconductor devices evenhaving miniature patterns can be tested at a high throughput, so that atotal inspection can also be conducted, thereby making it possible toimprove the yield rate of products and prevent defective products frombeing shipped. In this respect, description will be made with referenceto FIG. 4( b).

Generally, an electron beam based testing apparatus is expensive and lowin throughput as compared with other process apparatuses, so that such adefect testing apparatus is presently used after critical steps forwhich testing is most required (for example, etching, deposition or CMP(chemical-mechanical polishing) planarization processing). In thisevent, a wafer under testing is aligned on a super precise X-Y stagethrough an atmosphere transport system and a vacuum transport system,and fixed by an electrostatic chuck mechanism or the like. Subsequently,testing for defects and so on is conducted in accordance with aprocedure illustrated in FIG. 4( b).

In FIG. 4( b), first, an optical microscope is used to confirm theposition of each die, and detect the height of each location for storageas required. Other than this, the optical microscope is used to capturean optical microscopic image of a desired site such as defects forcomparison with an electron beam image. Next, information onprescription is input to the apparatus in accordance with the type of awafer (after which process, whether the size of the wafer is 20 cm or 30cm, and so on) to specify a testing location, set electron-opticalsystems, set testing conditions, and so on. Subsequently, the defecttesting is conducted generally in real time while images are captured.Through comparison of cells with one another, comparison of dies, and soon, a high speed information processing system installed with algorithmsconducts the testing to output the result to a CRT and so on and storesthe result in a memory as required.

Defects include particle defect, anomalous shape (pattern defect),electrical defects (disconnected wires or vias, defective conduction andthe like), and so on. Distinction of these defects, and classificationof the defects by size, and identification of killer defects (criticaldefects which disable chips to be used) may be automatically performedin real time.

The detection of electrical defects can be carried out by detectinganomalous potential contrasts. For example, a defectively conductedlocation is generally charged in positive by irradiation of electronbeams (at approximately 500 eV) and presents a lower contrast, so thatit can be distinguished from normal locations. An electron beamirradiating means in this case refers to a low potential (energy)electron beam generating means (generation of thermal electrons,UV/photoelectrons) which is separately provided for emphasizing thecontrast caused by a potential difference, other than the normalelectron beam irradiating means for testing. Before irradiating a regionunder testing with a testing electron beam, a low potential (energy)electron beam is generated for irradiation. For the projection systemwhich can positively charge a sample by irradiating the same with atesting electron beam, the low potential electron beam generating meansneed not be provided in separation depending on specifications. Also,defects can be detected from a difference in contrast which is producedby applying a sample such as a wafer with a positive or a negativepotential with respect to a reference potential (due to a difference inthe ease of flow in a forward direction or a backward direction of thedevice). Such a defect testing apparatus can be utilized as well in aline width measuring apparatus and an alignment precision measurement.

A method of testing electrical defects of a sample under testing maytake advantage of the fact that a voltage at an essentially electricallyinsulated portion is different from a voltage when this portion isconducted. For this purpose, charges are previously supplemented to asample under testing to produce a difference in potential between theessentially electrically insulated portion and a portion which shouldhave been electrically insulated but is conducted by some cause.Subsequently, a charged particle beam is irradiated from the chargedparticle beam apparatus according to the present invention to acquiredata with the difference in potential, and the acquired data is analyzedto detect the conducted state.

Embodiment Relating to Testing Apparatus Second Embodiment

The second embodiment of the present invention relates to an electronbeam apparatus suitable for testing, using an electron beam, defects inpatterns formed on the surface of an object under testing, and moreparticularly, to an electron beam apparatus suitable for a testingapparatus useful, for example, in detecting defects on a wafer in asemiconductor manufacturing process, which includes irradiating anobject under testing with an electron beam, capturing secondaryelectrons which vary in accordance with the properties of the surfacethereof to form image data, and testing patterns formed on the surfaceof the object under testing based on the image data at a highthroughput, and a method of manufacturing devices at a high yield rateusing such an electron beam apparatus.

As an apparatus for testing defects of a wafer using an electron beam,an apparatus using a scanning electron microscope (SEM) alreadycommercially available is known. This apparatus involves raster scanningan object under testing with a narrowed electron beam at very narrowintervals of raster width, detecting secondary electrons emitted fromthe object under testing associated with the scanning to form a SEMimage, and comparing such SEM images of different dies at the samelocations to extract defects of the object under testing.

Conventionally, however, there has been no electron beam based defecttesting apparatus which is completed as a general system.

A defect testing apparatus to which an SEM is applied requires a longtime for defect testing due to a small beam dimension, a resulting smallpixel dimension and a small raster width. In addition, a beam currentincreased for purposes of improving the throughput would cause chargingon a wafer having an insulating material formed on the surface thereof,thereby failing to produce satisfactory SEM images.

Hitherto, clarification has hardly been made for the overall structureof a testing apparatus which takes into account the relevancy of anelectron-optical device for irradiating an object under testing with anelectron beam for testing, and other subsystems associated therewith forsupplying the object under testing to an irradiating position of theelectron-optical device in a clean state and for aligning the objectunder testing. Further, with the trend of increasingly larger diametersof wafers which would be subjected to testing, the subsystems are alsorequired to support larger diameter wafers.

In view of the problems mentioned above, the second embodiment of thepresent invention has been proposed. It is an object of the presentinvention to provide

an electron beam apparatus which employs an electron beam basedelectron-optical system, and achieves harmonization of theelectron-optical system with other components, which constitute thetesting apparatus, to improve the throughput;

an electron beam apparatus which is capable of efficiently andaccurately testing an object under testing by improving a loader forcarrying the object under testing between a cassette for storing objectsunder testing and a stage device for aligning the object under testingwith respect to the electron-optical system, and devices associatedtherewith;

an electron beam apparatus which is capable of solving the problem ofcharging, experienced in the SEM, to accurately test an object undertesting; and

a method of manufacturing a device at a high yield rate by testing anobject under testing such as a wafer, using the electron beam apparatusdescribed above.

In the following, the second embodiment of a charged particle beamapparatus according to the present invention will be described withreference to the accompanying drawings, in connection with an overallstructure and operation of a semiconductor testing apparatus fortesting, as an object under testing, a substrate, i.e., a wafer whichhas patterns formed on the surface thereof, as well as in connectionwith a device manufacturing method using the semiconductor testingapparatus.

In FIGS. 5 and 6( a), a semiconductor testing apparatus 1 comprises acassette holder 10 for holding cassettes which stores a plurality ofwafers; a mini-environment chamber 20; a main housing 30 which defines aworking chamber; a loader housing 40 disposed between themini-environment chamber 20 and the main housing 30 to define twoloading chambers; a loader 60 for loading a wafer from the cassetteholder 10 onto a stage system 50 disposed in the main housing 30; and anelectron-optical system 70 installed in the vacuum main housing 30.These components are arranged in a positional relationship asillustrated in FIGS. 5 and 6( a). The semiconductor testing apparatus 1further comprises a precharge unit 81 disposed in the vacuum mainhousing 30; a potential applying mechanism 83 (see in FIG. 12) forapplying a wafer with a potential; an electron beam calibrationmechanism 85 (see in FIG. 13); and an optical microscope 871 which formspart of an alignment controller 87 for aligning the wafer on the stagesystem 50.

The cassette holder 10 is configured to hold a plurality (two in thisembodiment) of cassettes c (for example, closed cassettes such as FOUPmanufactured by Assist Co.) in which a plurality (for example,twenty-five) wafers are placed side by side in parallel, oriented in thevertical direction. The cassette holder 10 can be arbitrarily selectedfor installation adapted to a particular loading mechanism.Specifically, when a cassette, carried to the cassette holder 10, isautomatically loaded into the cassette holder 10 by a robot or the like,the cassette holder 10 having a structure adapted to the automaticlading can be installed. When a cassette is manually loaded into thecassette holder 10, the cassette holder 10 having an open cassettestructure can be installed. In this embodiment, the cassette holder 10is a type adapted to the automatic cassette loading, and comprises, forexample, an up/down table 11, and an elevating mechanism 12 for movingthe up/down table 11 up and down. The cassette c can be automaticallyset onto the up/down table 11 in a state indicated by chain lines inFIG. 6( a). After the setting, the cassette c is automatically rotatedto a state indicated by solid lines in FIG. 6( a) so that it is directedto the axis of pivotal movement of a first carrier unit within themini-environment chamber 20. In addition, the up/down table 11 is moveddown to a state indicated by chain lines in FIG. 5. In this way, thecassette holder 10 for use in automatic loading, or the cassette holder10 for use in manual loading may be both implemented by those in knownstructures, so that detailed description on their structures andfunctions are omitted.

FIG. 6( b) shows a modification to a mechanism for automatically loadinga cassette. A plurality of 300 mm wafers W are contained in a slottedpocket (not shown) fixed to the inner surface of a box body 501 forcarriage and storage. This wafer carrying box 28 comprises a box body501 of a squared cylinder, a wafer carrying in/out door 502 provided atan aperture 29 of a side surface of the box body 501 for communicatewith an automatic door opening apparatus and capable of being opened andclosed mechanically, a cap 503 positioned in opposite to the aperture 29to cover the aperture 29 for the purpose of detachably mounting filersand fan motors, a slotted pocket (not shown), an ULPA filter 505, achemical filter 506 and a fan motor 507. In this modification, wafers Ware carried in and out by means of a first carrying unit 612 of a robottype loader 60.

It should be noted that substrates, i.e., wafers accommodated in thecassette c are wafers subjected to testing which is generally performedafter a process for processing the wafers or in the middle of theprocess within semiconductor manufacturing processes. Specifically,accommodated in the cassette are substrates or wafers which haveundergone a deposition process, CMP, ion implantation and so on; waferseach formed with wiring patterns on the surface thereof; or wafers whichhave not been formed with wiring patterns. Since a large number ofwafers accommodated in the cassette c are spaced from each other in thevertical direction and arranged side by side in parallel, the firstcarrier unit has an arm which is vertically movable such that a wafer atan arbitrary position can be held by the first carrier unit, asdescribed later in detail.

In FIGS. 5 through 7, the mini-environment device 20 comprises a housing22 which defines a mini-environment space 21 that is controlled for theatmosphere; a gas circulator 23 for circulating a gas such as clean airwithin the mini-environment space 21 for the atmosphere control; adischarger 24 for recovering a portion of air supplied into themini-environment space 21 for discharging; and a pre-aligner 25 forroughly aligning a substrate, i.e., a wafer under testing, which isplaced in the mini-environment space 21.

The housing 22 has a top wall 221, a bottom wall 222, and peripheralwall 223 which surrounds four sides of the housing 22 to provide astructure for isolating the mini-environment space 21 from the outside.For controlling the atmosphere in the mini-environment space 21, the gascirculator 23 comprises a gas supply unit 231 attached to the top wall221 within the mini-environment space 21 as illustrated in FIG. 7 forcleaning a gas (air in this embodiment) and delivering the cleaned gasdownward through one or more gas nozzles (not shown) in laminar flow; arecovery duct 232 disposed on the bottom wall 222 within themini-environment space for recovering air which has flown down to thebottom; and a conduit 233 for connecting the recovery duct 232 to thegas supply unit 231 for returning recovered air to the gas supply unit231.

In this embodiment, the gas supply unit 231 takes about 20% of air to besupplied, from the outside of the housing 22 for cleaning. However, thepercentage of gas taken from the outside may be arbitrarily selected.The gas supply unit 231 comprises an HEPA or ULPA filter in a knownstructure for creating cleaned air. The laminar downflow of cleaned airis mainly supplied such that the air passes a carrying surface formed bythe first carrier unit, later described, disposed within themini-environment space 21 to prevent dust particles, which could beproduced by the carrier unit, from attaching to the wafer. Therefore,the downflow nozzles need not be positioned near the top wall asillustrated, but is only required to be above the carrying surfaceformed by the carrier unit. In addition, the air need not either besupplied over the entire mini-environment space 21.

It should be noted that an ion wind may be used as cleaned air to ensurethe cleanliness as the case may be. Also, a sensor may be providedwithin the mini-environment space 21 for observing the cleanliness suchthat the apparatus is shut down when the cleanliness is degraded.

An access port 225 is formed in a portion of the peripheral wall 223 ofthe housing 22 that is adjacent to the cassette holder 10. A shutterdevice in a known structure may be provided near the access port 225 toshut the access port 225 from the mini-environment device 20. Thelaminar downflow near the wafer may be, for example, at a rate of 0.3 to0.4 m/sec. The gas supply unit 231 may be disposed outside themini-environment space 21 instead of within the mini-environment space21.

The discharger 24 comprises a suction duct 241 disposed at a positionbelow the wafer carrying surface of the carrier unit and below thecarrier unit; a blower 242 disposed outside the housing 22; and aconduit 243 for connecting the suction duct 241 to the blower 242. Thedischarger 24 aspires a gas flowing down around the carrier unit andincluding dust, which could be produced by the carrier unit, through thesuction duct 241, and discharges the gas outside the housing 22 throughthe conduits 243, 244 and the blower 242. In this event, the gas may bedischarged into an exhaust pipe (not shown) which is laid to thevicinity of the housing 22.

The aligner 25 disposed within the mini-environment space 21 opticallyor mechanically detects an orientation flat (which refers to a flatportion formed along the outer periphery of a circular wafer andhereunder called as ori-fla) formed on the wafer, or one or moreV-shaped notches formed on the outer peripheral edge of the wafer topreviously align the position of the waver in a rotating direction aboutthe axis O-O at an accuracy of approximately ±one degree. Thepre-aligner forms part of a mechanism for determining the coordinates ofan object under testing, which is a feature of the claimed invention,and is responsible for rough alignment of an object under testing. Sincethe pre-aligner itself may be of a known structure, description on itsstructure and operation is omitted.

Though not shown, a recovery duct for the discharger 24 may also beprovided below the prealigner such that air including dust, dischargedfrom the prealigner, is discharged to the outside.

In FIGS. 5 and 6( a), the main housing 30, which defines the workingchamber 31, comprises a housing body 32 that is supported by a housingsupporting device 33 carried on a vibration isolator 37 disposed on abase frame 36. The housing supporting device 33 comprises a framestructure 331 assembled into a rectangular form. The housing body 32comprises a bottom wall 321 mounted on and securely carried on the framestructure 331; a top wall 322; and a peripheral wall 323 which isconnected to the bottom wall 321 and the top wall 322 and surrounds foursides of the housing body 32, and isolates the working chamber 31 fromthe outside. In this embodiment, the bottom wall 321 is made of arelatively thick steel plate to prevent distortion due to the weight ofequipment carried thereon such as the stage device 50. Alternatively,another structure may be employed.

In this embodiment, the housing body 32 and the housing supportingdevice 33 are assembled into a rigid construction, and the vibrationisolator 37 blocks vibrations from the floor, on which the base frame 36is installed, from being transmitted to the rigid structure. A portionof the peripheral wall 323 of the housing body 32 that adjoins theloader housing 40, later described, is formed with an access port 325for introducing and removing a wafer. The vibration isolator may beeither of an active type which has an air spring, a magnetic bearing andso on, or a passive type likewise having these components. Since anyknown structure may be employed for the vibration isolator, descriptionon the structure and functions of the vibration isolator itself isomitted. The working chamber 31 is held in a vacuum atmosphere by avacuum system (not shown) in a known structure.

A controller 2 for controlling the operation of the overall apparatus isdisposed below the base frame 36, and mainly comprises a maincontroller, a control controller and a stage controller.

The main controller has a man-machine interface through which theoperation by an operator (input of various instructions/commands andmenus, instruction to start a test, switch between automatic and manualtest modes, input of all commands necessary when the manual test mode)is performed. Further, the main controller performs a communication to ahost computer in a factory, control of a vacuum discharge system,carriage of a sample such as a wafer, control of alignment, transmissionof commands to the control controller and the stage controller andreceipt of information. Moreover, the main controller has a function ofobtaining an image signal from the optical microscope, a stage vibrationcorrecting function for feeding back a vibration signal of the stage tothe electron-optical system to correct a deteriorated image, and anautomatic focus correcting function for detecting a Z-direction (thedirection of the axis of the secondary optical system) displacement of asample observing position to feed back the displacement to theelectron-optical system so as to automatically correct the focus.Reception and transmission of a feedback signal to the electron-opticalsystem and a signal from the stage can be performed through the controlcontroller and the stage controller.

The control controller is mainly responsible for control of theelectron-optical system (control of an a highly accurate voltage sourcefor electron gun, lenses, alighners and Wien filter). Specifically, thecontrol controller effects control (gang control) of automatic voltagesetting to each lens system and the alighners in correspondence witheach operation mode, for example, causes a region to be irradiated by aconstant electron current even if the magnification is changed, andautomatically sets a voltage applied to each lens system and thealighners in correspondence with each magnification.

The stage controller is mainly responsible for control regarding themovement of the stage and enables the achievement of accurate X- andY-direction movement of micrometer order. Further, the stage controllerachieves control of rotation (θ control) of the stage within an erroraccuracy of ±0.3 seconds.

In FIGS. 5, 6(a) and 8, the loader housing 40 comprises a housing body43 which defines a first loading chamber 41 and a second loading chamber42. The housing body 43 comprises a bottom wall 431; a top wall 432; aperipheral wall 433 which surrounds four sides of the housing body 43;and a partition wall 434 for partitioning the first loading chamber 41and the second loading chamber 42 such that both the loading chamberscan be isolated from the outside. The partition wall 434 is formed withan opening, i.e., an access port 435 for passing a wafer between boththe loading chambers. Also, a portion of the peripheral wall 433 thatadjoins the mini-environment device 20 and the main housing 30 is formedwith access ports 436, 437. The housing body 43 of the loader housing 40is carried on and supported by the frame structure 331 of the housingsupporting device 33. This prevents the vibrations of the floor frombeing transmitted to the loader housing 40 as well.

The access port 436 of the loader housing 40 is in alignment with theaccess port 226 of the housing 22 of the mini-environment device 20, anda shutter device 27 is provided for selectively blocking a communicationbetween the mini-environment space 21 and the first loading chamber 41.The shutter device 27 has a sealing material 271 which surrounds theperipheries of the access ports 226, 436 and is fixed to the side wall433 in close contact therewith; a door 272 for blocking air from flowingthrough the access ports in cooperation with the sealing material 271;and a driver 273 for moving the door 272. Likewise, the access port 437of the loader housing 40 is in alignment with the access port 325 of thehousing body 32, and a shutter 45 is provided for selectively blocking acommunication between the second loading chamber 42 and the workingchamber 31 in a hermetic manner. The shutter 45 comprises a sealingmaterial 451 which surrounds the peripheries of the access ports 437,325 and is fixed to side walls 433, 323 in close contact therewith; adoor 452 for blocking air from flowing through the access ports incooperation with the sealing material 451; and a driver 453 for movingthe door 452.

Further, the opening formed through the partition wall 434 is providedwith a shutter 46 for closing the opening with the door 461 toselectively blocking a communication between the first and secondloading chambers in a hermetic manner. These shutter devices 27, 45, 46are configured to provide air-tight sealing for the respective chamberswhen they are in a closed state. Since these shutter devices may beimplemented by known ones, detailed description on their structures andoperations is omitted. It should be noted that a method of supportingthe housing 22 of the mini-environment chamber 20 is different from amethod of supporting the loader housing 40. Therefore, for preventingvibrations from being transmitted from the floor through themini-environment chamber 20 to the loader housing 40 and the mainhousing 30, a vibration-absorption cushion material may be disposedbetween the housing 22 and the loader housing 40 to provide air-tightsealing for the peripheries of the access ports.

Within the first loading chamber 41, a wafer rack 47 is disposed forsupporting a plurality (two in this embodiment) of wafers spaced in thevertical direction and maintained in a horizontal state. As illustratedin FIG. 9, the wafer rack 47 comprises posts 472 fixed at four cornersof a rectangular substrate 471, spaced from one another, in an uprightstate. Each of the posts 472 is formed with supporting devices 473, 474in two stages, such that peripheral edges of wafers W are carried on andheld by these supporting devices. Then, leading ends of arms of thefirst and second carrier units, later described, are brought closer towafers from adjacent posts and grab the wafers.

The loading chambers 41, 42 can be controlled for the atmosphere to bemaintained in a high vacuum state (at a vacuum degree of 10⁻⁵ to 10⁻⁶Pa) by a vacuum evacuator (not shown) in a known structure including avacuum pump, not shown. In this event, the first loading chamber 41 maybe held in a low vacuum atmosphere as a low vacuum chamber, while thesecond loading chamber 42 may be held in a high vacuum atmosphere as ahigh vacuum chamber, to effectively prevent contamination of wafers. Theemployment of such a structure allows a wafer, which is accommodated inthe loading chamber and is next subjected to the defect testing, to becarried into the working chamber without delay. The employment of such aloading chambers provides for an improved throughput for the defecttesting, and the highest possible vacuum state around the electronsource which is required to be kept in a high vacuum state, togetherwith the principle of a multi-beam type electron device, laterdescribed.

The vacuum exhaust system comprises a vacuum pump, a vacuum valve, avacuum gauge and a vacuum pipe for performing vacuum exhaust of theelectron-optical system, the detectors, the sample chamber and the loadlock chamber in accordance with a predetermined sequence. The vacuumvalve is controlled so as to achieve the degree of vacuum required bythe respective units. For this end, the degree of vacuum is monitored atany time, and an emergency control of a separation valve by aninterlocking mechanism is performed to maintain the degree of vacuum, ifany abnormality is found. As the vacuum pump, a turbo molecular pump isused for the main exhaust and a Roots dry pump is used for roughexhaust. The pressure at a test location (electron beam irradiatedregion) is 10⁻³ to 10⁻⁵ Pa. Preferably, pressure of 10⁻⁴ to 10⁻⁶ Pa ispractical.

The first and second loading chambers 41, 42 are connected to a vacuumexhaust pipe and a vent pipe for an inert gas (for example, dried purenitrogen) (neither of which are shown), respectively. In this way, theatmospheric state within each loading chamber is attained by an inertgas vent (which injects an inert gas to prevent an oxygen gas and so onother than the inert gas from attaching on the surface). Since anapparatus itself for implementing the inert gas vent is known instructure, detailed description thereon is omitted.

In the testing apparatus according to the present invention which usesan electron beam, when representative lanthanum hexaborate (LaB₆) usedas an electron source for an electron-optical system, later described,is once heated to such a high temperature that causes emission ofthermal electrons, it should not be exposed to oxygen within the limitsof possibility so as not to shorten the lifetime. The exposure to oxygencan be prevented without fail by carrying out the atmosphere control asmentioned above at a stage before introducing a wafer into the workingchamber in which the electron-optical system is disposed.

The stage device 50 comprises a fixed table 51 disposed on the bottomwall 301 of the main housing 30; a Y-table 52 movable in a Y-directionon the fixed table 51 (the direction vertical to the drawing sheet inFIG. 5); an X-table 53 movable in an X-direction on the Y-table 52 (inthe left-to-right direction in FIG. 1); a turntable 54 rotatable on theX-table; and a holder 55 disposed on the turntable 54. A wafer isreleasably held on a wafer carrying surface 551 of the holder 55. Theholder 55 may be of a known structure which is capable of releasablygrabbing a wafer by means of a mechanical or electrostatic chuckfeature.

The stage device 50 uses servo motors, encoders and a variety of sensors(not shown) to operate a plurality of tables as mentioned above topermit highly accurate alignment of a wafer held on the carrying surface551 by the holder 55 in the X-direction, Y-direction and Z-direction (inthe up-down direction in FIG. 5) with respect to an electron beamirradiated from the electron-optical system, and in a direction aboutthe axis normal to the wafer supporting surface (θ direction). Thealignment in the Z-direction may be made such that the position on thecarrying surface 551 of the holder 55, for example, can be finelyadjusted in the Z-direction. In this event, a reference position on thecarrying surface 551 is sensed by a position measuring device using alaser of an extremely small diameter (a laser interference range finderusing the principles of interferometer) to control the position by afeedback circuit, not shown. Additionally or alternatively, the positionof a notch or an orientation flat of a wafer is measured to sense aplane position or a rotational position of the wafer relative to theelectron beam to control the position of the wafer by rotating theturntable 54 by a stepping motor which can be controlled in extremelysmall angular increments.

In order to maximally prevent dust produced within the working chamber,servo motors 531, 531 and encoders 522, 532 for the stage device 50 aredisposed outside the main housing 30. Since the stage system 50 may beof a known structure used, for example, in steppers and so on, detaileddescription on its structure and operation is omitted. Likewise, sincethe laser interference range finder may also be of a known structure,detailed description on its structure and operation is omitted.

It is also possible to establish a basis for signals which are generatedby previously inputting a rotational position, and X-, Y-positions of awafer relative to the electron beam in a signal detecting system or animage processing system, later described. The wafer chucking mechanismprovided in the holder 55 is configured to apply a voltage for chuckinga wafer to an electrode of an electrostatic chuck, and the alignment ismade by pinning three points on the outer periphery of the wafer(preferably spaced equally in the circumferential direction). The waferchucking mechanism comprises two fixed aligning pins and a push-typeclamp pin. The clamp pin can implement automatic chucking and automaticreleasing, and constitutes a conducting spot for applying the voltage.

While in this embodiment, the X-table is defined as a table which ismovable in the left-to-right direction in FIG. 6( a); and the Y-table asa table which is movable in the up-down direction, a table movable inthe left-to-right direction in FIG. 2 may be defined as the Y-table; anda table movable in the up-down direction as the X-table.

The loader 60 comprises a robot-type first carrier unit 61 disposedwithin the housing 22 of the mini-environment chamber 20; and arobot-type second carrier unit 63 disposed within the second loadingchamber 42.

The first carrier unit 61 comprises a multi-node arm 612 rotatable aboutan axis O₁-O₁ with respect to a driver 611. While an arbitrary structuremay be used for the multi-node arm, the multi-node arm in thisembodiment has three parts which are pivotably attached to each other.One part of the arm 612 of the first carrier unit 61, i.e., the firstpart closest to the driver 611 is attached to a rotatable shaft 613 by adriving mechanism (not shown) of a known structure, disposed within thedriver 611. The arm 612 is pivotable about the axis O₁-O₁ by means ofthe shaft 613, and radially telescopic as a whole with respect to theaxis O₁-O₁ through relative rotations among the parts. At a leading endof the third part of the arm 612 furthest away from the shaft 613, agrabber 616 in a known structure for grabbing a wafer, such as amechanical chuck or an electrostatic chuck, is disposed. The driver 611is movable in the vertical direction by an elevating mechanism 615 of aknown structure.

The first carrier unit 61 extends the arm 612 in either a direction M1or a direction M2 within two cassettes c held in the cassette holder 10,and removes a wafer accommodated in a cassette c by carrying the waferon the arm or by grabbing the wafer with the chuck (not shown) attachedat the leading end of the arm. Subsequently, the arm is retracted (in astate as illustrated in FIG. 6( a)), and then rotated to a position atwhich the arm can extend in a direction M3 toward the prealigner 25, andstopped at this position. Then, the arm is again extended to transferthe wafer held on the arm to the prealigner 25. After receiving a waferfrom the prealigner 25, contrary to the foregoing, the arm is furtherrotated and stopped at a position at which it can extend to the secondloading chamber 41 (in the direction M4), and transfers the wafer to awafer receiver 47 within the second loading chamber 41.

For mechanically grabbing a wafer, the wafer should be grabbed on aperipheral region (in a range of approximately 5 mm from the peripheraledge). This is because the wafer is formed with devices (circuitpatterns) over the entire surface except for the peripheral region, andgrabbing the inner region would result in failed or defective devices.

The second carrier unit 63 is basically identical to the first carrierunit 61 in structure except that the second carrier unit 63 carries awafer between the wafer rack 47 and the carrying surface of the stagedevice 50, so that detailed description thereon is omitted.

In the loader 60, the first and second carrier units 61, 63 each carry awafer from a cassette held in the cassette holder 10 to the stage device50 disposed in the working chamber 31 and vice versa, while remainingsubstantially in a horizontal state. The arms of the carrier units aremoved in the vertical direction only when a wafer is removed from andinserted into a cassette, when a wafer is carried on and removed fromthe wafer rack, and when a wafer is carried on and removed from thestage device 50. It is therefore possible to smoothly carry a largerwafer, for example, a wafer having a diameter of 30 cm.

Next, how a wafer is carried will be described in sequence from thecassette c held by the cassette holder 10 to the stage device 50disposed in the working chamber 31.

As described above, when the cassette is manually set, the cassetteholder 10 having a structure adapted to the manual setting is used, andwhen the cassette is automatically set, the cassette holder 10 having astructure adapted to the automatic setting is used. In this embodiment,as the cassette c is set on the up/down table 11 of the cassette holder10, the up/down table 11 is moved down by the elevating mechanism 12 toalign the cassette c with the access port 225.

As the cassette is aligned with the access port 225, a cover (not shown)provided for the cassette is opened, and a cylindrical cover is appliedbetween the cassette c and the access port 225 of the mini-environmentto block the cassette and the mini-environment space 21 from theoutside. Since these structures are known, detailed description on theirstructures and operations is omitted. When the mini-environment device20 is provided with a shutter for opening and closing the access port225, the shutter is operated to open the access port 225.

On the other hand, the arm 612 of the first carrier unit 61 remainsoriented in either the direction M1 or M2 (in the direction M1 in thisdescription). As the access port 225 is opened, the arm 612 extends toreceive one of wafers accommodated in the cassette at the leading end.While the arm and a wafer to be removed from the cassette are adjustedin the vertical position by moving up or down the driver 611 of thefirst carrier unit 61 and the arm 612 in this embodiment, the adjustmentmay be made by moving up and down the up/down table 11 of the cassetteholder 10, or made by both.

As the arm 612 has received the wafer, the arm 621 is retracted, and theshutter is operated to close the access port (when the shutter isprovided). Next, the arm 612 is pivoted about the axis O₁-O₁ such thatit can extend in the direction M3. Then, the arm 612 is extended andtransfers the wafer carried at the leading end or grabbed by the chuckonto the prealigner 25 which aligns the orientation of the rotatingdirection of the wafer (the direction about the central axis vertical tothe wafer plane) within a predetermined range. Upon completion of thealignment, the carrier unit 61 retracts the arm 612 after a wafer hasbeen received from the prealigner 25 to the leading end of the arm 612,and takes a posture in which the arm 612 can be extended in a directionM4. Then, the door 272 of the shutter device 27 is moved to open theaccess ports 223, 236, and the arm 612 is extended to place the wafer onthe upper stage or the lower stage of the wafer rack 47 within the firstloading chamber 41. It should be noted that before the shutter device 27opens the access ports to transfer the wafer to the wafer rack 47, theopening 435 formed through the partition wall 434 is closed by the door461 of the shutter 46 in an air-tight state.

In the process of carrying a wafer by the first carrier unit, clean airflows (as downflow) in laminar flow from the gas supply unit 231disposed on the housing of the mini-environment chamber to prevent dustfrom attaching on the upper surface of the wafer during the carriage. Aportion of the air near the carrier unit (in this embodiment, about 20%of the air supplied from the supply unit 231, mainly contaminated air)is aspired from the suction duct 241 of the discharger 24 and dischargedoutside the housing. The remaining air is recovered through the recoveryduct 232 disposed on the bottom of the housing and returned again to thegas supply unit 231.

As the wafer is placed into the wafer rack 47 within the first loadingchamber 41 of the loader housing 40 by the first carrier unit 61, theshutter device 27 is closed to seal the loading chamber 41. Then, thefirst loading chamber 41 is filled with an inert gas to expel air.Subsequently, the inert gas is also discharged so that a vacuumatmosphere dominates within the loading chamber 41. The vacuumatmosphere within the loading chamber 41 may be at a low vacuum degree.When a certain degree of vacuum is provided within the loading chamber41, the shutter 46 is operated to open the access port 434 which hasbeen sealed by the door 461, and the arm 632 of the second carrier unit63 is extended to receive one wafer from the wafer receiver 47 with thegrabber at the leading end (the wafer is carried on the leading end orgrabbed by the chuck attached to the leading end). Upon completion ofthe receipt of the wafer, the arm 632 is retracted, followed by theshutter 46 again operated to close the access port 435 by the door 461.

It should be noted that the arm 632 has previously taken a posture inwhich it can extend in the direction N1 of the wafer rack 47 before theshutter 46 is operated to open the access port 435. Also, as describedabove, the access ports 437, 325 have been closed by the door 452 of theshutter 45 before the shutter 46 is operated to block the communicationbetween the second loading chamber 42 and the working chamber 31 in anair-tight state, so that the second loading chamber 42 is evacuated.

As the shutter 46 is operated to close the access port 435, the secondloading chamber 42 is again evacuated at a higher degree of vacuum thanthe first loading chamber 41. Meanwhile, the arm 632 of the secondcarrier unit 63 is rotated to a position at which it can extend towardthe stage device 50 within the working chamber 31. On the other hand, inthe stage device 50 within the working chamber 31, the Y-table 52 ismoved upward, as viewed in FIG. 6( a), to a position at which the centerline O₀-O₀ of the X-table 53 substantially matches an X-axis X₁-X₁ whichpasses a pivotal axis O₂-O₂ of the second carrier unit 63. The X-table53 in turn is moved to the position closest to the leftmost position inFIG. 6( a), and remains awaiting at this position.

When the second loading chamber 42 is evacuated to substantially thesame degree of vacuum as the working chamber 31, the door 452 of theshutter 45 is moved to open the access ports 437, 325, allowing the arm632 to extend so that the leading end of the arm 632, which holds awafer, approaches the stage device 50 within the working chamber 31.Then, the wafer is placed on the carrying surface 551 of the stagedevice 50. As the wafer has been placed on the carrying surface 551, thearm 632 is retracted, followed by the gate 45 operated to close theaccess ports 437, 325.

The foregoing description has been made on the operation until a waferin the cassette c is carried and placed on the stage device 50. Forreturning a wafer, which has been carried on the stage device 50 andprocessed, from the stage device 50 to the cassette c, the operationreverse to the foregoing is performed. Since a plurality of wafers arestored in the wafer rack 47, the first carrier unit 61 can carry a waferbetween the cassette and the wafer rack 47 while the second carrier unit63 is carrying a wafer between the wafer rack 47 and the stage device50, so that the testing operation can be efficiently carried out.

Specifically, if a wafer A and a wafer B, both processed already, areplaced on the wafer rack 47 of the second carrier unit, the wafer B notprocessed is moved to the stage device 50 and a process starts. In themiddle of the process, the processed wafer A is moved to the wafer rack47 from the stage device 50. A unprocessed wafer C is likewise extractedfrom the wafer rack 47 by the arm and is aligned by the prealinghner.Then, the wafer C is moved to the wafer rack 47 of the loading chamber41. By doing so, it is possible to replace the wafer A with theunprocessed wafer C in the wafer rack 47 during the wafer B is beingprocessed.

Depending upon how such an apparatus for performing a test or evaluationis utilized, a plurality of the stage devices 50 can be disposed causinga wafer to be transferred from one wafer rack 47 to each stage device,making it possible to process a plurality of wafers in a similar manner.

FIG. 10 illustrates an exemplary modification to the method ofsupporting the main housing. In an exemplary modification illustrated inFIG. 10[A], a housing supporting device 33 a is made of a thickrectangular steel plate 331 a, and a housing body 32 a is carried on thesteel plate. Therefore, the bottom wall 321 a of the housing body 32 ais thinner than the bottom wall 222 of the housing body 32 in theforegoing embodiment.

In an exemplary modification illustrated in FIG. 10[B], a housing body32 b and a loader housing 40 b are suspended by a frame structure 336 bof a housing supporting device 33 b. Lower ends of a plurality ofvertical frames 337 b fixed to the frame structure 336 b are fixed tofour corners of a bottom wall 321 b of the housing body 32 b, such thatthe peripheral wall and the top wall are supported by the bottom wall. Avibration isolator 37 b is disposed between the frame structure 336 band a base frame 36 b. Likewise, the loader housing 40 is suspended by asuspending member 49 b fixed to the frame structure 336. In theexemplary modification of the housing body 32 b illustrated in FIG.10[B], the housing body 32 b is supported in suspension, the generalcenter of gravity of the main housing and a variety of devices disposedtherein can be brought downward. The methods of supporting the mainhousing and the loader housing, including the exemplary modificationsdescribed above, are configured to prevent vibrations from beingtransmitted from the floor to the main housing and the loader housing.

In another exemplary modification, not shown, the housing body of themain housing is only supported by the housing supporting device frombelow, while the loader housing may be placed on the floor in the sameway as the adjacent mini-environment chamber. Alternatively, in afurther exemplary modification, not shown, the housing body of the mainhousing is only supported by the frame structure in suspension, whilethe loader housing may be placed on the floor in the same way as theadjacent mini-environment device.

The electron-optical device 70 comprises a column 71 fixed on thehousing body 32. Disposed within the column 71 are an electron-opticalsystem comprised of a primary electron-optical system (hereinaftersimply called the “primary optical system”) 72 and a secondaryelectron-optical system (hereinafter simply called the “secondaryoptical system”) 74, and a detecting system 76, as illustrated generallyin FIG. 11. The primary optical system 72, which is an optical systemfor irradiating the surface of a wafer W under testing with an electronbeam, comprises an electron gun 721 for emitting an electron beam; alens system 722 comprised of electrostatic lenses for converging aprimary electron beam emitted from the electron gun 721; a Wien filter(i.e., an ExB separator or an ExB filter) 723; and an objective lenssystem 724. These components are arranged in order with the electron gun721 placed at the top, as illustrated in FIG. 11. The lensesconstituting the objective lens system 724 in this embodiment aredeceleration electric field type objective lenses. In this embodiment,the optical axis of the primary electron beam emitted from the electrongun 721 is oblique to the optical axis of irradiation along which thewafer W under testing is irradiated with the electron beam (vertical tothe surface of the wafer). Electrodes 725 are disposed between theobjective lens system 724 and the wafer W under testing. The electrodes27 are axially symmetric about the optical axis of irradiation of theprimary electron beam, and controlled in voltage by a power supply 726.

The secondary optical system 74 comprises a lens system 741 comprised ofelectrostatic lenses which pass secondary electrons separated from theprimary optical system by an ExB deflector 723. This lens system 741functions as a magnifier for enlarging a secondary electron image.

The detecting system 76 comprises a detector 761 and a detector 763which are disposed on a focal plane of the lens system 741.

Next, the operation of the electron-optical device 70 configured asdescribed above will be described.

The primary electron beam emitted from the electron gun 721 is convergedby the lens system 722. The converged primary electron beam impinges onthe ExB deflector 723, is deflected so that it is irradiated vertical tothe surface of the wafer W, and focused on the surface of the wafer W bythe objective lens system 724.

The secondary electrons emitted from the wafer by the irradiation of theprimary electron beam are accelerated by the objective lens system 724,impinge on the ExB deflector 723, travels straight through the deflector723, and are lead to the detector 761 by the lens system 741 of thesecondary optical system. Then, the secondary electrons are detected bythe detector 761 which generates a detection signal to an imageprocessing unit 763.

Assume in this embodiment that the objective lens system 724 is appliedwith a high voltage in a range of 10 to 20 kV, and a wafer has beenprepared in place.

Here, when the electrodes 725 are applied with a voltage of −200 V ifthe wafer W includes a via b, an electric field of 0 to −0.1 V/mm (“−”indicates that the wafer W has a higher potential) is produced on thesurface of the wafer W irradiated with the electron beam. In this state,although the wafer W can be tested for defects without causing adischarge between the objective lens system 724 and the wafer W, aslight degradation is experienced in the efficiency of detecting thesecondary electrons. Therefore, a sequence of operations involvingirradiating the electron beam and detecting the secondary electrons isperformed, for example, four times, such that the results of the fourdetections are applied with processing such as accumulative addition,averaging and so on to obtain a predetermined detection sensitivity.

On the other hand, when the wafer is free from the via b, no dischargeis caused between the objective lens system 724 and the wafer even ifthe electrodes 725 are applied with a voltage of +350, so that the waferW can be tested for defects. In this event, since the secondaryelectrons are converged by the voltage applied to the electrodes 725 andfurther converged by the objective lens 724, the detector 761 has animproved efficiency of detecting the secondary electrons. Consequently,the processing as the wafer defect detector is performed at a higherspeed, so that the testing can be made at a higher throughput.

The precharge unit 81, as illustrated in FIG. 5, is disposed adjacent tothe barrel 71 of the electron-optical device 70 within the workingchamber 31. Since this testing apparatus is configured to test asubstrate or a wafer under testing for device patterns or the likeformed on the surface thereof by irradiating the wafer with an electronbeam, so that the secondary electrons emitted by the irradiation of theelectron beam are used as information on the surface of the wafer.However, the surface of the wafer may be charged up depending onconditions such as the wafer material, energy of the irradiatedelectrons, and so on. Further, even on the surface of a single wafer,some region may be highly charged, while another region may be lowlycharged. Variations in the amount of charge on the surface of the waferwould cause corresponding variations in information provided by theresulting secondary electrons, thereby failing to acquire correctinformation.

For preventing such variations, in this embodiment, the precharge unit81 is provided with a charged particle irradiating unit 811. Beforetesting electrons are irradiated to a predetermined region on a waferunder testing, charged particles are irradiated from the chargedparticle irradiating unit 811 of the precharge unit 81 to eliminatevariations in charge. The charges on the surface of the wafer previouslyform an image of the surface of the wafer under testing, which image isevaluated to detect possible variations in charge to operate theprecharge unit 81 based on the detection.

Alternatively, the precharge unit 81 may irradiate a blurred primaryelectron beam.

Referring next to FIG. 12, the potential applying mechanism 83 applies apotential of ±several volts to a carrier of a stage, on which the waferis placed, to control the generation of secondary electrons based on thefact that the information on the secondary electrons emitted from thewafer (secondary electron generating rate) depend on the potential onthe wafer. The potential applying mechanism 83 also serves to deceleratethe energy originally possessed by irradiated electrons to provide thewafer with irradiated electron energy of approximately 100 to 500 eV.

As illustrated in FIG. 12, the potential applying mechanism 83 comprisesa voltage applying device 831 electrically connected to the carryingsurface 541 of the stage device 50; and a charging examining/voltagedetermining system (hereinafter examining/determining system) 832. Theexamining/determining system 832 comprises a monitor 833 electricallyconnected to an image forming unit 763 of the detecting system 76 in theelectron-optical device 70; an operator 834 connected to the monitor833; and a CPU 835 connected to the operator 834. The CPU 835 supplies asignal to the voltage applying device 831.

The potential applying mechanism 83 is designed to find a potential atwhich the wafer under testing is hardly charged, and to apply suchpotential to the carrying surface 541.

Referring next to FIG. 13, the electron beam calibration mechanism 85comprises a plurality of Faraday cups 851, 852 for measuring a beamcurrent, disposed at a plurality of positions in a lateral region of thewafer carrying surface 541 on the turntable 54. The Faraday cups 851 areprovided for a narrow beam (approximately φ2 μm), while the Faraday cups852 for a wide beam (approximately φ30 μm). The Faraday cuts 851 for anarrow beam measure a beam profile by driving the turntable 54 step bystep, while the Faraday cups 852 for a wide beam measure a total amountof currents. The Faraday cups 851, 852 are mounted on the wafer carryingsurface 541 such that their top surfaces are coplanar with the uppersurface of the wafer W carried on the carrying surface 541. In this way,the primary electron beam emitted from the electron gun 721 is monitoredat all times. This is because the electron gun 721 cannot emit aconstant electron beam at all times but varies in the emission currentas it is used over time.

The alignment controller 87, which aligns the wafer W with theelectron-optical device 70 using the stage device 50, performs thecontrol for rough alignment through wide field observation using theoptical microscope 871 (a measurement with a lower magnification than ameasurement made by the electron-optical system); high magnificationalignment using the electron-optical system of the electron-opticaldevice 70; focus adjustment; testing region setting; pattern alignment;and so on. The wafer is tested at a low magnification using the opticalsystem in this way because an alignment mark must be readily detected byan electron beam when the wafer is aligned by observing patterns on thewafer in a narrow field using the electron beam for automaticallytesting the wafer for patterns thereon.

The optical microscope 871 is disposed on the housing 30 (alternatively,may be movably disposed within the housing 30), with a light source, notshown, being additionally disposed within the housing 30 for operatingthe optical microscope. The electron-optical system for observing thewafer at a high magnification shares the electron-optical systems(primary optical system 72 and secondary optical system 74) of theelectron-optical device 70. The configuration may be generallyillustrated in FIG. 12. For observing a point of interest on a wafer ata low magnification, the X-stage 53 of the stage device 50 is moved inthe X-direction to move the point of interest on the wafer into a viewfield of the optical microscope 871. The wafer is viewed in a wide fieldby the optical microscope 871, and the point of interest on the wafer tobe observed is displayed on a monitor 873 through a CCD 872 to roughlydetermine a position to be observed. In this event, the magnification ofthe optical microscope may be changed from a low magnification to a highmagnification.

Next, the stage device 50 is moved by a distance corresponding to aspacing δx between the optical axis of the electron-optical device 70and the optical axis of the optical microscope 871 to move the point onthe wafer under observation, previously determined by the opticalmicroscope 871, to a point in the view field of the electron-opticaldevice 70. In this event, since the distance δx between the axis O₃-O₃of the electron-optical device and the axis O₄-O₄ of the opticalmicroscope 871 is previously known (while it is assumed that theelectron-optical device 70 is deviated from the optical microscope 871in the direction along the X-axis in this embodiment, they may bedeviated in the Y-axis direction as well as in the X-axis direction),the point under observation can be moved to the viewing position bymoving the stage device 50 by the distance δx. After the point underobservation has been moved to the viewing position of theelectron-optical device 70, the point under observation is imaged by theelectron-optical system at a high magnification for storing a resultingimage or displaying the image on the monitor 765 through the CCD 761.

After the point under observation on the wafer imaged by theelectron-optical system at a high magnification is displayed on themonitor 765, misalignment of the stage device 50 with respect to thecenter of rotation of the turntable 54 in the wafer rotating direction,and misalignment δθ of the stage device 50 with respect to the opticalaxis O₃-O₃ of the electron-optical system in the wafer rotatingdirection are detected in a known method, and misalignment of apredetermined pattern with respect to the electron-optical device in theX-axis and Y-axis is also detected. Then, the operation of the stagedevice 50 is controlled to align the wafer based on the detected valuesand data on a testing mark attached on the wafer or data on the shape ofthe patterns on the wafer which have been acquired in separation.

The testing apparatus as described with reference to FIGS. 5 to 14, usedin the wafer testing process (G) in the device manufacturing methoddescribed with reference to FIGS. 3 and 4( a) and 4(b), can detectsemiconductor devices having fine patterns with high throughput, therebyenabling all wafers to be tested, the yield rate of the products to beimproved and defective products to be prevented from being shipped. Inthis regards, the description made with reference to FIGS. 3, 4(a) and4(b) is incorporated herewith by reference and is omitted hereaccordingly.

Embodiment Relating to Column Third Embodiment

Now, an electron beam apparatus, which is a third embodiment of theelectron beam apparatus according to the present invention, will bedescribed with reference to FIG. 15. This electron beam apparatus issuitable for evaluating and testing samples such as wafers, masks and soon which have patterns with a minimum line width of 0.1 micron or lessat a high throughput and high reliability, and can be used formanufacturing of devices.

An electron beam apparatus using multi-beams is already known. Forexample, a known electron beam apparatus emits one or more electronbeams converged to a predetermined diameter from an electron beam sourcewhich is focused on the surface of a sample under testing, moves thesample under testing to scan the electron beams on the surface of thesample under testing, detects secondary electron beams emitted from thesample under testing and reflected electron beams using a plurality ofdetecting devices, and simultaneously or parallelly processes outputs ofthe detecting devices to reduce a time required for evaluating miniaturepatterns.

Also, a known miniature pattern evaluation apparatus irradiates a sampleunder testing with a plurality of primary electron beams, detectssecondary electron beams emitted as the result and reflected electronbeams for each primary electron beam, and adjusts voltages on electrodesand excitation currents for each primary electron beam, in order toeliminate variations in the spot shapes of electron beams emitted from aplurality of electron beam sources to improve the precision of theevaluation on miniature patterns.

In such a multi-beam based electron beam apparatus, the electron beamsource section requires a different degree of vacuum from alens/deflection system. For example, in a multi-emitter or thermal fieldemission type electron beam source, a safe operation is not ensuredunless the degree of vacuum higher than 10⁻⁸ torr is provided near acathode of the electron beam source, while the lens/deflection systemcan sufficiently operate if the degree of vacuum on the order of 10⁻⁶torr is achieved even in case an electrostatic lens and an electrostaticdeflector are used. There is therefore a problem that a predetermineddegree of vacuum must be maintained for each component of the electronbeam apparatus.

Also, since an extremely large number of ions exist on the optical axisof the electron beam within a column of an electron microscope, anotherproblem is that positive ions collide with the cathode of the electronbeam source to perforate the cathode. Further, actually, no clearsolution has been given to a problem of how respective columns are fixedwhen a multi-beam and multi-column electron beam apparatus is to bemanufactured.

An electron beam apparatus illustrated in FIG. 15, which has beenproposed to solve the problems mentioned above, is characterized byholding a high degree of vacuum in an electron beam source section evenwhen the degree of vacuum is low in a lens/deflection system, therebypreventing damages of the cathode of the electron beam source and makingitself resistant to vibrations.

In FIG. 15, the electron beam apparatus has a multi-beam/multi-columnstructure, wherein an electron beam source section X and anelectron-optical system Y are separated by a thick partition wall Swhich has both ends fixed to a column (not shown). The electron beamsource section X comprises a plurality of electron beam source chambers901, each in a cylindrical shape, mutually coupled by a bellows 902.Each of the electron beam source chambers 901 comprises a thermal fieldemission type electron beam source 905 which is comprised of a TFEcathode 903 and a Schottky shield 904. Each of the electron beam sources905 is powered through a high voltage cable 906, and emits an electronbeam from the TFE cathode 903. TFE is an acronym of thermal fieldemission.

Each of the electron beam source chamber 901 is fixed to the partitionwall S with a screw 907. Therefore, the partition wall S needs to have apredetermined thickness to have a sufficient rigidity. If the partitionwall S is not sufficient in rigidity, a reinforcing rib is desirablydisposed between adjacent electron beam source chambers 901. Each of theelectron beam source chambers 901 is connected to an ion pump (notshown) for evacuation.

The partition wall S is formed with a predetermined number, for example,four of holes 908 on a circumference about the optical axis of theelectron beam source 905 of each electron beam source chamber 901 suchthat electron beams emitted from surfaces of tungsten <301> or <100>orientation surface of the TFE cathode 3 in the respective electron beamsources 905 can fully pass through the partition wall S. These holes 908each have a large aspect ratio (ratio of the diameter of the hole to thelength of the hole) so as not to deteriorate the degree of vacuum in theelectron beam source chamber, and is formed to have a larger diameter asit is further away from the TFE cathode 903. Alternatively, each of theholes 908 may be obliquely formed in a direction away from the opticalaxis at a lower location. Generally, the aspect ratio may preferably be10 or more.

On the other hand, the electron-optical system Y has a lens/deflectionsystem 910 arranged corresponding to each of the electron beam sourcechambers 901 in order to reshape each of electron beams emitted from theplurality of electron beam source chambers 901 such that a sample W suchas a wafer is irradiated with the plurality of electron beams. Each ofthe lens/deflection system 910 comprises an elongated pipe 909 fixed tothe partition wall S with a screw 911 so as to surround, for example,the four holes 908 which allow electron beams from correspondingelectron beam sources 905 to pass therethrough. In each of the pipes909, a required lens and deflector are arranged for reshaping electronbeams, which have passed through, for example, the four holes 908 of thepartition wall S, and for directing them perpendicular to the sample W.In this way, the multi-column electron-optical system Y is configured.

Thus, each lens/deflection system 910 has, within the pipe 909, acondenser lens 912, a multi-aperture plate 913, a reduction lens 914, adeflector 915 and an objective lens 916 arranged in order. The condenserlenses 912 converge electron beams which have passed through therespective holes 908 formed through the partition wall S. Themulti-aperture plates 913 comprise a number of small holes equal to theholes 908 in the portion of the partition wall S surrounded by the pipe909 so as to pass therethrough the electron beams converged by thecondenser lenses 912. The reduction lenses 914 reduce the dimension andinterval of the electron beams, which have passed through themulti-aperture plate 913, so that they pass through the deflectors 915.The deflector 915 changes the direction in which the electron beamtravels such that the electron beam reduced by the reduction lens 914scans on the sample. The objective lens 916 focuses the electron beampassing through the deflector 915 on the sample W.

Each of the pipes 909 is provided with an exhaust hole 917 through whichthe interior of each pipe 909 is held at a vacuum by a pump formaintaining the interior of the column (not shown), which houses thepartition wall S, electron beam source section Y and electron-opticalsystem Y at a vacuum. Also, the condenser lens 912, multi-aperture plate913, reduction lens 914, deflector 915 and objective lens 916 areapplied with required voltages through lead lines illustrated by dottedlines in FIG. 15. The condenser lens 912, multi-aperture plate 913,reduction lens 914, deflector 915 and objective lens 916 are attached onthe inner wall of the pipe 909 through an insulating spacer 918, asrequired.

The electron beam apparatus illustrated in FIG. 15 can be used in thetesting process (G) described with reference to FIG. 3 and FIGS. 4( a),4(b) as an evaluation apparatus for testing for defects, measurement ofline widths, measurement of alignment precision, measurement ofpotential contrast, defect review, or strobe SEM in order to evaluate awafer in the middle of the process. In this regard, the descriptionrelated to FIG. 3 and FIGS. 4( a), 4(b) is incorporated herewith byreference and is omitted here accordingly.

Embodiment Relating to Structure of Electrodes Fourth Embodiment

A fourth embodiment of the present invention relates to an electron beamapparatus which comprises an electrode structure for preventing thebreakdown in an electron-optical system which uses an electrostatic lensfor irradiating a sample with an electron beam, and a devicemanufacturing method using this apparatus.

Up to now, studies have been made for applying a high sensitivity, highresolution electron beam apparatus which utilizes electron beams inorder to test a surface state of a fine pattern for which opticaltesting alone cannot be relied on to provide sufficient sensitivity andresolution.

Such an electron beam apparatus emits an electron beam from an electronbeam source, accelerates and converges the emitted electron beam by anelectrostatic optical system such as an electrostatic lens, and directsthe electron beam to a sample or an object under testing. Next, asecondary electron beam emitted from the sample by the incident electronbeam is detected to generate a signal corresponding to the detectedsecondary electron beam, and data on the sample, for example, is formedfrom this signal. The surface state of the sample is tested using theformed data.

In an electron-optical system using an electrostatic lens such as anelectrostatic lens for use in such an electron beam apparatus,electrodes for generating an electric field for accelerating orconverging an electron beam are arranged in the direction of the opticalaxis of the electron beam at multiple stages. These electrodes are eachapplied with a predetermined voltage, such that the electron beam isaccelerated or converged at a predetermined point on the optical axis bythe electric field generated due to a difference in potential on theelectrodes.

In a conventional electron beam apparatus, a portion of electron beamsemitted from an electron beam source may collide with electrodesirrespective of an electric field in an electron-optical system using anelectrostatic lens. In this event, the electron beams collide withelectrodes to emit secondary electron beams from the electrodesthemselves. The amount of secondary electron beams emitted from theelectrodes depends on the material of the electrodes or a materialcoated on the electrodes. As a larger number of secondary electron beamsare emitted from the electrodes, the secondary electron beams areaccelerated by the electric field of the electrodes to ionize a residualgas within the apparatus. Then, the ions collide with the electrodes,causing further secondary electron beams to be emitted from theelectrodes. Therefore, as a large amount of secondary electron beams areemitted, a discharge is more likely to occur between electrodes,resulting in an increased probability of breakdown between electrodes.

For example, comparing the probability of breakdown between an electrodecoated with aluminum and an electrode coated with gold, the probabilityof breakdown is slightly higher with the aluminum coated electrode.Aluminum has a work function of 4.2 [eV], while gold has a work functionof 4.9 [eV]. Here, the work function refers to minimum energy requiredto draw out one electron within the metal into a vacuum (unit: eV).

Also, when an electrode is coated with gold, and a sample in theelectron beam apparatus is a semiconductor wafer, the gold is sputteredby electron beams colliding with the coated gold, resulting in the goldattached on the surface of the semiconductor wafer. The gold attached onthe surface of the semiconductor would be diffused into silicon crystalsin subsequent thermal processes, resulting in deteriorated performanceof transistors. Therefore, in this case, the electron beam apparatus isnot suitable for testing a semiconductor wafer.

On the other hand, in an electrostatic lens, for example, of anelectron-optical system using the electrostatic lens, the distancebetween electrodes is reduced to provide an electrostatic lens with ashort focal distance. A shorter focal distance reduces an aberrationcoefficient of the electrostatic lens and is of low aberration, with theresult that the electrostatic lens has a high resolution and that theevaluation apparatus is improved in resolution.

Alternatively, an electrostatic lens with a short focal distance can beprovided by increasing potential differences applied between electrodesof the electrostatic lens. Thus, as is the case of reducing the distancebetween electrodes, the electrostatic lens exhibits low aberration andhigh resolution, so that the electron beam apparatus is improved inresolution. As such, with a reduced distance between electrodes andlarger potential differences between electrodes, the electrostatic lenscan be synergistically provided with lower aberration and higherresolution. However, a shorter distance between electrodes and a largerpotential difference between the electrodes would result in a problem ofhigher susceptibility to a discharge between the electrodes and anincreased probability of breakdown between the electrodes.

Conventionally, an insulating material is inserted between electrodeswhich are supported by the insulating material, to hold insulationbetween the electrodes. Also, the insulating performance on the surfaceof the insulating material is improved by increasing a minimum creepingdistance (insulating surface length) of the insulating material betweenthe electrodes. For example, the minimum creeping distance betweenelectrodes is increased, for example, by forming the surface of aninsulating material in the shape of crimps in the direction along theelectrodes.

However, the surface of an insulating material is generally difficult inworking as compared with a metal, so that the working cost becomeshigher. Also, the surface of the insulating material formed in a crimpshape or the like results in a larger surface area of the insulatingarea, so that gases emitted from the insulating material may increasewhen a vacuum is held in the electron beam apparatus. Therefore, in manycases, the degree of vacuum is reduced, resulting in a lower resistancevoltage between electrodes on the contrary.

The fourth embodiment of the present invention has been proposed tosolve such problems. In the following, the configuration and operationof a projection type evaluation apparatus having an electrostaticoptical system, and a device manufacturing method using the apparatuswill be described for the case where the projection type evaluationapparatus is applied with the electron beam apparatus which is capableof preventing the breakdown between electrodes in the electrostaticoptical system according to the present invention.

In FIG. 16, in a projection type evaluation apparatus 1000, an electronbeam irradiated to a sample has a predetermined irradiation face, and asecondary electron beam radiated from the sample irradiated with theelectron beam also has a predetermined radiation face. From an electronbeam source 1001, an electron beam having a two-dimensional region, forexample, a rectangular radiation face is irradiated and deflected by anelectrostatic lens system 1002 in a predetermined direction. Thedeflected electron beam is directed to an ExB deflector 1003 diagonallyfrom above, and is deflected in the direction of a semiconductor wafer1006, which is a sample, by a field in which an electric and magneticfield of the ExB deflector 1003 are produced orthogonal to each other (asolid line in FIG. 16).

The electron beam deflected toward the semiconductor wafer 1006 by theExB deflector 1003 is decelerated by an electric field generated byvoltages applied to electrodes within the electrostatic objective lenssystem 1005, and focused on the semiconductor wafer 1006 by theelectrostatic objective lens 1005.

Next, a secondary electron beam generated by the irradiation of theelectron beam to the semiconductor wafer 1006 is accelerated by theelectric field of the electrostatic objective lens system 1005 in thedirection of a detector 1008 (a dotted line in FIG. 16), and directedinto the ExB deflector 1003. The ExB deflector 1003 redirects theaccelerated secondary electron beam toward an electrostatic intermediatelens system 1007. Next, the electrostatic intermediate lens system 1007directs the secondary electron beam into the detector 1008 to detect thesecondary electron beam. The secondary electron beam detected by thedetector 1008 is converted into data which is transmitted to a displaydevice 1009, and an image of the secondary electron beam is displayed onthe display device 1009 for testing patterns on the semiconductor wafer1006.

Next, described in detail will be the configuration of the electrostaticlens system 1002, electrostatic objective lens 1005, electrostaticintermediate lens system 1007 and ExB deflector 1003 in the projectiontype evaluation apparatus 1000. The electrostatic lens system 1002 andelectrostatic objective lens system 1005, through which an electron beampasses, and the electrostatic intermediate lens system 1007, throughwhich a secondary electron beam passes, include a plurality ofelectrodes for generating predetermined electric fields. Also, all ofthese electrodes are coated with platinum on their surfaces. Further,electrodes 1004 of the ExB deflector 1003 are also coated with platinumon their surfaces.

Now, a breakdown occurrence probability will be described for each ofmetals coated on electrodes with reference to FIG. 17. The breakdownoccurrence probability is represented by a relative hierarchicalrelationship for each metal. Also, it is assumed that in the projectiontype evaluation apparatus, other testing conditions are identical exceptfor the type of metal coated on electrodes.

First, comparing the probability of producing the breakdown between anelectrode coated with aluminum and an electrode coated with gold, theelectrode coated with gold exhibited a slightly lower probability ofbreakdown. Therefore, the gold is more effective in preventing thebreakdown. Further, comparing the probability of producing the breakdownbetween an electrode coated with gold and an electrode coated withplatinum, the electrode coated with platinum exhibited a yet lowerprobability of breakdown.

Here, in regard to the work function of each metal, aluminum has a workfunction of 4.2 [eV]; gold 4.9 [eV], and platinum 5.3[eV]. Here, thework function refers to minimum energy required to draw out one electronbeam within the metal into a vacuum (unit:eV). In other words, as thevalue of work function is larger, an electron beam is more difficult todraw out.

Therefore, in the map projection type evaluation apparatus 1000, when anelectron beam emitted from the electron beam source 1001 collides withan electrode, a less amount of secondary electron beam will be emittedfrom the electrode if the electrode is coated with a metal having alarge value of work function (including an alloy made of a metal havinga large value of work function as a main material), so that theprobability of producing the breakdown of the electrode is reduced. Forthis reason, a metal having a large work function is preferable tocertain extent. Specifically, when an electrode is coated with a metalhaving a work function equal to 5 [eV], it is possible to suppress theprobability of producing the breakdown of the electrode.

Also, when a sample under testing is the semiconductor 1006 and anelectrode is coated with gold, as in this embodiment, an electron beammay collide with gold in some cases to result in the gold attached onpatterns of the semiconductor wafer 1006. Therefore, if the electrode iscoated with platinum in this embodiment, no platinum will be attached onpatterns of the semiconductor wafer 1006. Even attachment of platinumwould not deteriorate the device performance. In addition, theoccurrence of producing the breakdown of the electrode is reduced, sothat the electrode coated with platinum is more preferable.

Next, an example of the shape and structure of electrodes will bedescribed with reference to FIGS. 18 and 19. In FIG. 18, electrodes 1010are electrodes of an electrostatic lens included in the electrostaticlens system 1002, electrostatic objective lens system 1005 andelectrostatic intermediate lens system 1007.

The electrodes 1010 are in the shape of disk formed with a throughholesubstantially at the center thereof, through which an electron beam anda secondary electron beam can pass. In the projection type evaluationapparatus 1000 of this embodiment, the electrodes 1010 are applied witha predetermined voltage by a power supply, not shown.

FIG. 19 is a partial cross-sectional view of a surface portion of anelectrode 1010. The surface of the electrode 1004 in the ExB deflector1003 may have an equivalent structure to the surface of the electrode1010. A material for the electrodes 1010 comprises silicon bronze 1010a. Titanium 1010 b is sputter coated in a thickness of 50 nm on thesilicon bronze 1010 a worked into a required dimensional shape, andplatinum 1010 c is further sputter coated in a thickness of 200 nm onthe titanium 1010 b to form the electrode 1010.

Now, the structure of electrodes for preventing a breakdown between theelectrodes when a large potential difference is present between theelectrodes in this embodiment will be described in detail with referenceto FIGS. 20 and 21. Electrodes 1020, 1022 in FIG. 20 are electrodesincluded, for example, in the electrostatic objective lens system 1005,and platinum is coated on the electrodes, as mentioned above. Also, theelectrodes 1020, 1022 are applied with predetermined voltages by a powersupply, not shown. In this embodiment, the electrode 1022 on thesemiconductor wafer 1006 side is applied with a high voltage, forexample, a voltage of 15 kV, while the electrode 1020 is applied with avoltage of 5 kV.

Throughholes 1024, through which the electron beam and secondaryelectron beam pass, are formed in central portions of the electrodes1020, 1022, and an electric field is formed within the throughhole 1024by a potential difference between the electrodes 1020, 1022. Electronbeams are decelerated and converged by this electric field, andirradiated to the semiconductor wafer 1006. In this event, since thepotential difference between the electrodes is large, an electrostaticobjective lens having a short focal distance can be used for theelectrostatic objective lens system 1005. Consequently, theelectrostatic objective lens system 1005 exhibits low aberration andhigh resolution.

An insulating spacer 1026 is inserted between the electrodes 1020 and1022, where the insulating spacer 1026 substantially vertically supportsthe electrodes 1020, 1022. A minimum creeping distance of the insulatingspacer 1026 between the electrodes is substantially the same as thedistance between portions of the electrodes supported by the insulatingspacer 1026. In other words, the surface of the insulating spacer 1026between the electrodes is not formed in the shape of crimps in thedirection along the electrodes but substantially in a linear shape.

The electrode 1022 has a first electrode surface 1022 b at a minimumdistance between the electrodes, a second electrode surface 1022 chaving an inter-electrode distance longer than the first electrodesurface 1022 b, and a step 1022 d (FIG. 21) between the first electrodesurface 1022 b and the second electrode surface 1022 c in the directionalong these two electrodes. The insulating spacer 1026 supports theelectrode 1022 on the second electrode surface 1022 c.

Since the electrode 1022 is shaped as described, it is possible to makethe minimum creeping distance of the insulating spacer 1026 longer thanthe minimum distance between the electrodes while holding the minimumdistance between the electrodes at a predetermined distance, withoutcreating crimps or the like on the surface of the insulating spacer 1026in the direction along the electrodes. Also, since the surface of theinsulating spacer 1026 is not applied with a large electric field, theresulting structure is less susceptible to a creeping discharge.

Consequently, the electrostatic objective lens system 1005 can be anelectrostatic objective lens with a short focal distance, low aberrationand high resolution, and the insulating performance of the insulatingspacer 1026 is not degraded between the electrodes, so that thebreakdown between the electrodes can be prevented. Further, since themetal-made electrode 1022 is worked to have the step 1022 d, a workingcost is less expensive than working the insulating spacer 1026. Inaddition, the surface of the insulating spacer 1026 is substantiallyfree of ruggedness in the direction along the electrodes, so that gasesemitted from the insulating spacer 1026 will not be increased.

Furthermore, since corner portions between an open end 1020 a of thethrough hole 1024 of the electrode 1020 and an open end 1022 a of thethroughhole 1024 of the electrode 1022 are formed with curvatures, noelectric field will be concentrate on both corner portions, so that thebreakdown between the electrodes can be more reliably prevented.Moreover, since a corner portion of the step 1022 d of the electrode1022 between the electrodes is formed with a curvature, no electricfield will be concentrate on both corner portions, so that the breakdownbetween the electrodes can be more reliably prevented.

While in the fourth embodiment, the step 1022 d is formed in theelectrode 1022, the electrode 1020 may also be worked to have a steptoward the electrode 1022, or in place of the electrode 1022, theelectrode 1020 alone may be worked to have a step toward the electrode1022. Also, while the electrodes having the insulating spacer 1026inserted therebetween has been described in the electrostatic objectivelens system 1005, the insulating spacer may be applied to anotherelectrostatic lens system, if it includes electrodes with a largepotential difference generated therebetween, thereby making it possibleto prevent a breakdown between the electrodes.

The fourth embodiment described with reference to FIGS. 16-21 can beused in the testing process (G) in the device manufacturing methodpreviously described with reference to FIG. 3 and FIGS. 4( a), 4(b) toevaluate a semiconductor wafer without causing a breakdown betweenelectrodes in any electrostatic lens system. In this regard, thedescription related to FIG. 3 and FIGS. 4( a), 4(b) is cited, so thatdescription herein is omitted.

Embodiment Relating to Deflection Fifth Embodiment

A fifth embodiment of the present invention relates to an electron beamapparatus which is capable of performing testing for defects on patternswith a minimum line width of 0.2 micrometers or less, measurement ofline widths, measurement of alignment precision, stopgap measurement,high time resolution potential contrast measurement, and so on at a highthroughput and high reliability, and a device manufacturing method usingthe apparatus.

A known electron beam apparatus employs a Wien filter to separate aprimary electron beam from a secondary electron beam emitted from asample irradiated with the primary electron beam. For example, a knownelectron beam apparatus emits a primary electron beam from an electronbeam source such that it forms a predetermined angle with respect to theoptical axis perpendicular to a sample, deflects the travellingdirection of the primary electron beam by a Wien filter so as to goalong the optical axis such that the primary electron beam impingesperpendicularly on the sample, and separates a secondary electron beamemitted from the sample from the primary electron beam by the Wienfilter to force the secondary electron beam to travel along the opticalaxis and impinge on a detector. Also, another known electron beamapparatus directs a primary electron beam perpendicularly into a sample,separates a secondary electron beam emitted thereby from the sample byan ExB separator from the primary electron beam and inputs the secondaryelectron beam to a detector.

Such conventional electron beam apparatuses have a problem of inabilityto narrow down a beam comprised of primary electron radiations since theprimary electron beams having a large energy width are deflected atdifferent angles by the ExB separator depending on the magnitude ofenergy possessed by the primary electron radiations, causing chromatismin the primary electron beams. The problem of chromatism is also foundin an electron beam apparatus which forces a secondary electron beamemitted from a sample irradiated with a primary electron beam tolinearly impinge on a detector along the optical axis. When thesecondary electron beam emitted from a sample has a wide energy width,chromatism is generated when the secondary electron beam passes througha secondary optical system, thereby adversely affecting accuratedetection of the secondary electron beam.

The fifth embodiment of the present invention has been proposed to solvethe problems of the conventional electron beam apparatuses as mentionedabove, and provides a means for largely reducing the effect ofchromatism on a Wien filter in an electron beam apparatus which narrowsdown the primary electron beam for scanning a sample, or for largelyreducing chromatism caused by the energy width of the secondary electronbeam in an electron beam apparatus which projects an image of thesecondary electron beam for detection.

Also, the fifth embodiment of the present invention is suitable for adefect testing apparatus and so on which use the electron beam apparatuswhich achieves a reduction in chromatism as mentioned. Further, a waferin the middle of a process can be tested using such a defect testingapparatus and so on in a device manufacturing method.

In FIG. 22, a primary system including an electron beam source, and asecondary system including a detector are arranged opposite to eachother with respect to the optical axis X perpendicular to a sample, at apredetermined angle formed therebetween. In FIG. 22, a primary electronbeam 1102 emitted from the electron beam source 1101 is reshaped into arectangle by an opening (not shown), reduced by lenses 1103, 1104, andimpinges on a Wien filter 1105. In this event, assume that the angleformed by the primary electron beam 1012 to the optical axis X is 3α.

Specifically, the Wien filter 1105 comprises electrodes 1106 forcreating an electric field for electrostatic deflection, and a magnet1107 for creating a magnetic field for electromagnetic deflection. TheWien filter 1105 deflects the primary electron beams 1102 incidentthereon to the left, i.e., closer to the optical axis X by an angle α byan electrostatic deflecting action of the electrodes 1106, and deflectsthe primary electron beam 1102 to the left by an angle 2α by anelectromagnetic deflecting action of the magnet 1107, i.e., deflects theprimary electron beam 1102 to the left totally by the angle 3□, andforces the deflected primary electron beam 1102 to travel along theoptical axis X perpendicular to a sample 1108. Subsequently, the primaryelectron beam 1102 impinges on the sample 1108 through lens systems1109, 1110 and is irradiated to the sample 1108. The angle α is, forexample, 10 degrees.

A secondary electron beam 1111 emitted from the sample 1108 by theirradiation of the primary electron beam 1102 is enlarged by the lenssystems 1109, 1110, and then impinges on the Wien filter 1105 whichdeflects the secondary electron beam 1111 to the right by α degrees fromthe optical axis X, i.e., further away from the optical axis by theaction of its electrode 1106 and magnet 1107. The secondary electronbeam 1111 separated from the primary electron beams by the Wien filter1105 is enlarged by a secondary optical system including lens systems1112, 1113, and focused on a detector 1114. The output of the detector1114 is processed as appropriated by an image processing unit 1115 andstored in an image memory 1116.

In the fifth embodiment, chromatism caused by the Wien filter 1105 ismore problematic in the secondary optical system for processing thesecondary electron beams 1111. Thus, for eliminating the influence ofthe chromatism caused by the Wien filter 1105 on the secondary electronbeam 1111, the Wien filter 1105 is arranged such that its electrostaticdeflecting action and electromagnetic deflecting action deflect thesecondary electron beams in direction opposite to each other, and suchthat a predetermined relationship is established between an angle bywhich the secondary electron beam is deflected by the electrostaticdeflecting action and an angle by which the secondary electron beam isdeflected by the electromagnetic deflecting action. In this way, thesecondary electron beam 1111 emitted from the sample 1108 and travelingalong the optical axis X is deflected by a predetermined angle in thedirection opposite to the primary electron beams 1102 with respect tothe optical axis X, and in this event, the chromatism due to an energywidth possessed by the secondary electron beam 1111 can be reduced to aneglectable magnitude.

Thus, when the secondary electron beams 1111 impinges on the Wien filter1105, the electrode 1106 of the Wien filter 1105 deflects the secondaryelectron beam 1111 to the left, i.e., closer to the optical axis X by anangle □ by the electrostatic deflecting action, while the magnet 1107deflects the secondary electron beam 1111 to the right, i.e., furtheraway from the optical axis X by an angle 2□. In this event, assumingthat the beam energy of the secondary electron beams incident on theWien filter 1105 is Vo, a secondary electron beam having energy smallerthan Vo by ΔV is deflected by the electrodes 1106 by an angle:

α/(1−ΔV/Vo)=β

to the left from the optical axis, i.e., closer to the optical axis X.Simultaneously, the secondary electron beam 1111 having energy smallerthan Vo by ΔV is deflected by the magnet 1107 by an angle:

2α/{1−(ΔV/Vo)}^(1/2)=γ

to the right with respect to the optical axis X, i.e., further away fromthe optical axis X. In a primary approximation:

(1−ΔV/Vo)⁻¹=(1+ΔV/Vo); and

2{(1−ΔV/Vo)}^(−1/2)=2{1+(½)(ΔV/Vo)}

are derived, so that the following equation is established:

γ−β=2α{1+(½)(ΔV/Vo)}−α(1+ΔV/Vo)=α

Stated another way, a term related to the energy width of the secondaryelectron beam is erased by canceling the electrostatic deflecting actionand the electromagnetic deflecting action of the Wien filter 1105, sothat the secondary electron beam 111 is deflected by the Wien filter1105 to the right with respect to the optical axis X, i.e., further awayfrom the optical axis X by the angle α, thereby making it possible toneglect the chromatism caused by the Wien filter 1105.

FIG. 23 is a diagram illustrating in detail the configuration of thefifth embodiment of the present invention. In FIG. 23, a primaryelectron beam 1102 emitted from an electron beam source 1101 isconverged to an opening of a blanking opening plate 1121 by a condenserlens 1120. The primary electron beam 1102 passes an opening plate 1122having a large number of openings before traveling to the opening plate1121, whereby the primary electron beam 1102 is transformed intomultiple beams having a desired number of thin beams. The multipleprimary electron beams 1102 pass through the opening plate 1121, arereduced to beams of a predetermined dimension by reduction lenses 1123,1124 to form a reduced image 1122′, and then enter the Wien filter 1105.In this event, the angle of the primary electron beams 1102 formed withthe optical axis X is α. The primary electron beams 1102 are deflectedby the Wien filter 1105 by the angle α, travel along the optical axis Xperpendicular to the sample 1108, and are reduced by an objective lens1125 and symmetric electrodes 1126 and irradiated to the sample 1108.

For scanning the sample 1108 in a direction perpendicular to a directionin which openings are arranged on the opening plate 1122 (in FIG. 23,the direction perpendicular to the sheet) with the primary electronbeams 1102 exiting the Wien filter 1105, scanning electrodes 1127, 1128are placed along the optical path of the primary electron beams 1102.Also, blanking deflectors 1130, 11131 are arranged for deviating thetraveling direction of the primary electron beams 1102 from a normaltraveling direction during a blanking period such that the primaryelectron beams 1102 travel along an optical path 1129.

The sample 1108 emits secondary electron beams 1111 from respectivelocations irradiated respectively with a plurality of thin beams whichconstitute the primary electron beams 1102. The multiple secondaryelectron beams 1111 thus emitted are separated from the primary electronbeams by the Wien filter 1105, enlarged by focusing electron-opticalsystems 1132, 1133, pass through an opening plate 1134 having openingscorresponding to the openings of the opening plate 1122, and impinge onmultiple detectors 1135. Here illustrated in FIG. 23 is that the openingplate 1122 and opening plate 1134 are rotated by 90° about the opticalaxis.

While the chromatism caused by the Wien filter 1105 is also problematicfor the primary electron beams and secondary electron beams in thiscase, the influence of the chromatism generated in the secondary opticalsystem can be reduced by extending mutual intervals of the plurality ofbeams which constitute the multiple beams.

On the other hand, for eliminating the influence exerted by thechromatism caused by the Wien filter 1105 on the primary electron beams1102, in FIG. 23, the Wien filter 1105 is arranged such that itselectrostatic deflecting action and electromagnetic deflecting actiondeflect the primary electron beams in direction opposite to each other,and such that a predetermined relationship is established between anangle by which the primary electron beams are deflected by theelectrostatic deflecting action and an angle by which the primaryelectron beams are deflected by the electromagnetic deflecting action.In this way, the primary electron beams 1112 emitted from the electronbeam source 1101 and traveling obliquely with respect to the opticalaxis X are deflected by a predetermined angle to the left with respectto the optical axis X, i.e., closer to the optical axis X, and in thisevent, the chromatism due to an energy width possessed by the primaryelectron beams 1102 can be reduced to a neglectable magnitude.

Specifically describing the foregoing, the Wien filter 1105 deflects theprimary electron beams 1102 to the right, i.e., further away from theoptical axis by an angle α by the electrostatic deflecting action of theelectrodes 1106, and deflects the primary electron beams 1102 to theleft, i.e., closer to the optical axis X by an angle 2α by theelectromagnetic deflecting action of the magnet 1107. As a result, theprimary electron beams 1102, which have impinged on the Wien filter1105, are deflected to the left by an angle α as a whole. In this event,it is possible to neglect the influence of an energy width possessed bythe primary electron beams 1102. Specifically, the chromatism caused byan extended energy width of the primary electron beams 1102 iseliminated.

Explaining in a mathematical point of view, assuming that the beamenergy of the secondary electron beams incident on the Wien filter 1105is Vo, a primary electron beam having energy smaller than Vo by ΔV isdeflected by the electrodes 1106 by an angle:

α/(1−ΔV/Vo)=δ

Since this value is larger than α, the primary electron beam isdeflected additionally to the right, i.e., further away from the opticalaxis X. Simultaneously, the primary electron beam having energy smallerthan Vo by ΔV is deflected by the magnet 1107 by an angle:

2α{1−(ΔV/Vo)}^(−1/2)=θ

Since this value is larger than 2α, the primary electron beams aredeflected additionally to the left, i.e., closer to the optical axis X.Thus, the difference between these angles is calculated as follows:

θ−δ=2α{1−(ΔV/Vo)}^(−1/2)−α(1−ΔV/Vo)⁻¹

Since ΔV is extremely smaller than Vo:

(1−ΔV/Vo)^(−1/2)=(1+ΔV/2Vo)

is established as a primary approximation, so that eventually,

θ−δ=2α(1−ΔV/2Vo)−α(1−ΔV/Vo)=α

is established. In this way, when the primary electron beams 1102 aredeflected by the Wien filter 1105 by an angle α closer to the opticalaxis X, the energy width possessed by the primary electron beams can beneglected, thereby making it possible to eliminate the chromatism causedby the Wien filter 1105.

When a plurality of beams constituting the primary electron beams 1102are arranged on a single column and are deflected by the Wien filter1105 in a direction perpendicular to a direction in which these beamsare arranged, the chromatism generated in the secondary optical systemappears in the direction perpendicular to the beam arranged direction,so that crosstalk between the plurality of beams will not be increasedby the chromatism.

The electron beam apparatus described with reference to FIGS. 22 and 23can be applied to a variety of apparatuses such as a defect detectingapparatus, an alignment precision measuring apparatus, a line widthmeasuring apparatus, a high time resolution potential contrast measuringapparatus, a defect review apparatus, and strobe SEM apparatus. Also,the electron beam apparatus of the fifth embodiment can be used in thetesting process (G) in the device manufacturing method described inFIGS. 3 and 4( a), 4(b) in order to evaluate a wafer in the middle of aprocess. In this regard, the description related to FIG. 3 and FIGS. 4(a), 4(b) is incorporated herewith by reference and is omitted herein.

While the fifth embodiment of the present invention has been described,the present invention is not limited to such an embodiment. For example,a plurality of electron beam irradiation/detection systems, eachcomprised of an electron beam source, a primary optical system, asecondary optical system and a detector may be provided in order tosimultaneously irradiate different locations on the sample 1108, whereinthe sample is irradiated with a plurality of primary electron beamsemitted from the plurality of electron beam sources, and a plurality ofsecondary electron beams emitted from the sample are received by aplurality of detectors. This can largely reduce a time required for thetesting and measurements.

Embodiment Relating to Driving of Objective Lens Sixth Embodiment

A sixth embodiment of the present invention relates to an electron beamapparatus which is capable of performing a variety of evaluations fortesting for defects on patterns having line widths of 0.1 micron orless, CD measurements, alignment precision measurement, potentialmeasurement at a high time resolution, and so on at a high throughput,high accuracy and high reliability, and a device manufacturing methodusing this apparatus.

When patterns formed on the surface of a sample such as a semiconductorwafer is evaluated at a high accuracy using the result of scanning by anelectron beam, it is necessary to take into consideration variations inthe height of the sample. This is because the varying height of thesample results in a change in the distance between patterns on thesurface of the sample and an objective lens for converging the electronbeam on the patterns to cause a lower resolution due to dissatisfactionof a focusing condition, thereby failing to provide correct evaluation.

To eliminate this problem, a known electron beam apparatus directs lightobliquely into the surface of a sample, measures the height of thesample by use of the reflected light, feeds back the result ofmeasurement to an electron-optical system for converging an electronbeam to the sample to control currents and voltages supplied tocomponents of the electron-optical system, and thereby focuses theelectron-optical system.

However, a system which directs light obliquely into a sample requiresoptics mainly made of an insulating material which should be placed in aspace between the surface of the sample and the lower surface of theelectron-optical system for reflecting incident light. For this purpose,the spacing between the surface of the sample and the lower surface ofthe electron-optical system must be ensured more than necessity, whichhowever makes the problems such as the aberration of theelectron-optical system unneglectable. Presently, however, there is nomeans which simultaneously focuses the electron-optical system andeliminates the problems such as the aberration of the electron-opticalsystem.

The focusing of the electron-optical system must be performed inconsideration of not only the distance between the surface of the sampleand the lower surface of the electron-optical system but also a chargingstate on the surface of the sample, and space charge effect of electronbeams, so that errors might occur unless parameters related to thefocusing of the electron-optical system are electron-optically measured.

Further, when the electron-optical system is focused by adjusting anexcitation current for a magnetic lens included in the electron-opticalsystem, it is necessary to take a long time period from setting of theexcitation current to a predetermined value to stable establishment ofthe focal distance of the electron-optical system, i.e., a long settlingtime, thereby presenting a problem that it is difficult to perform thefocusing at a high speed. Otherwise, when the electron-optical system isfocused by changing an excitation voltage for an electrostatic lens, ahigh voltage applied to the electrostatic lens must be changed, therebysimilarly presenting a problem that a long settling time is required.

The sixth embodiment of the present invention provides an electron beamapparatus which is capable of electron-optically focusing theelectron-optical system in a short time, and a device manufacturingmethod using this apparatus for solving the foregoing problems.

FIG. 24 generally illustrates the configuration of the sixth embodimentof the present invention. In FIG. 24, an electron beam source 1201comprises an anode 1202. An emitted primary electron beam is acceleratedby the anode 1202 and passes through a small hole 1207 of an openingplate 1206 by way of deflectors 1203, 1204 for alignment, andastigmatism correcting lens 1205. The primary electron beam passingthrough the opening plate 1206 is converged by a condenser lens 1208,passes through a Wien filter 1211 by way of deflectors 1209, 1210, isreduced by an objective lens 1212, passes through axially symmetricelectrodes 1213, and is focused on one of a plurality of rectangularcircuit patterns, for example, formed on the surface of a sample 1214carried on a stage S. The axially symmetric electrodes 1213 are placedwith substantially no space between itself and the sample 1214. Thestage S is movable in a second direction perpendicular to a firstdirection in which the primary electron beam is deflected, so that thecircuit patterns are scanned by the deflection of the primary electronbeam and movements of the stage S.

As a result of the scanning using the primary electron beam, a secondaryelectron beam emitted from a circuit pattern on the sample 1214 isattracted and accelerated by an electric field of the objective lens1212, and deflected by the Wien filter 1211 such that it deviates froman optical axis L, so that the secondary electron beam is separated fromthe primary electron beam. Eventually, the secondary electron beam isdetected by a secondary electron beam detector 1085. The secondaryelectron beam detector 1215 outputs an electric signal indicative of theintensity of the incident secondary electron beam. This electric signalis amplified by a corresponding amplifier (not shown), and processed forgenerating an image.

For the condenser lens 1208 to reduce the primary electron beam,respective electrodes forming part of the condenser lens 1208 areapplied with required voltages from a first power supply 1217. Theobjective lens 1212 in turn is a uni-potential lens. For converging theprimary electron beam on the surface of the sample 1214, a centralelectrode of the objective lens 1212 is applied with a positive highvoltage Vo (volts) from a second power supply 1218, while an upperelectrode and a lower electrode of the objective lens 1212 are appliedwith small voltages ±ΔVo from a third power supply 1219.

The electron beam source 1201, anode 1202, deflectors 1203, 1204 foralignment, astigmatism correcting lens 1205, aperture plate 1206,condenser lens 1208, deflectors 1209, 1210, Wien filter 1211, objectivelens 1212, axially symmetric electrode 1213, and secondary electron beamdetector 1215 are housed in a column 1216 of a suitable size toconstitute a single electron beam scanning/detection system 1220.Initial focusing of the electron beam scanning/detection system 1220 canbe performed by changing the positive voltage Vo while fixing thevoltages ±ΔVo, for example, at −10 volts.

As described above, the electron beam scanning/detection system 1220scans one of chip patterns on the sample 1214, detects a secondaryelectron beam emitted from the sample 1214 as the result of thescanning, and outputs an electric signal indicative of its intensity.Actually, since the sample 1214 is formed with a plurality of chippatterns on its surface, electron beam scanning/detection systems (notshown) similar in configuration to the electron beam scanning/detectionsystem 1220 are arranged in parallel with the electron beamscanning/detection system 1220 such that the mutual distance is equal toan integer multiple of the dimension of one chip on the sample 1214.

Describing further on the electron beam scanning/detection system 1220,the electric signal output from the secondary electron beam detector1215 is converted into binary information, and this binary informationis converted to image data. As a result, image data representative ofthe circuit pattern formed on the surface of the sample 1214 can beacquired. The acquired image data is stored in a suitable storage meansand is compared with a reference pattern. In this way, defects on thecircuit pattern formed on the sample 1214 can be detected.

A variety of reference circuit patterns may be used for comparison withthe image data representative of a certain circuit pattern on the sample1214. For example, it is possible to use image data produced from CADdata for fabricating the circuit patterns which have been scanned togenerate the image data.

In the electron beam apparatus illustrated in FIG. 24, the values ofvoltages ±Vo applied to the upper electrode and lower electrode of theobjective lens 1212 are determined under control of a controller (notshown) such as a CPU in the following manner. First, a location at whicha pattern edge parallel to a first direction in which the primaryelectron beam is deflected and a pattern edge parallel to a seconddirection perpendicular to the first direction exist on an arbitrarycircuit pattern formed on the surface of the sample 1214 is read, forexample, from pattern data.

Next, using the deflectors 1209, 1210 and the Wien filter 1211, thepattern edge parallel to the first direction is scanned by the primaryelectron beam in the second direction, and an electric signal indicativeof the intensity of a secondary electron beam emitted as the result isobtained from the secondary electron beam detector 1215 to measure arising width (unit: microns) of the electric signal. Similarly, thepattern edge parallel to the second direction is also scanned in thefirst direction by the primary electron beam using the deflectors 1209,1210 and the Wien filter 1211, and an electric signal indicative of theintensity of a secondary electron beam emitted as the result is obtainedfrom the secondary electron beam detector 1215 to measure a rising widthof the secondary electron beam. This operation is performed each timethe values of the voltages ±ΔVo are changed. In this way, graphs A and Bshown in FIG. 25( a) are derived.

The aforementioned “rising width of the electric signal” refers to ascanning distance (in units of microns) in the second direction requiredfor the electric signal measured when the pattern edge parallel to thefirst direction is scanned in the second direction to change from 12% to88% of its maximum value, with the voltage ±ΔVo fixed at a certainvalue, as shown in FIG. 25( b).

In FIG. 25( a), the graph A shows that the voltage ΔVo is minimum at−ΔVo(x), i.e., the rising is the sharpest. Similarly, the graph B showsthat the voltage ΔVo is minimum at +ΔVo(x), i.e., the rising is thesharpest. Therefore, the focusing condition for the objective lens 1212,i.e., the values of the voltages ±ΔVo applied to the upper electrode andlower electrode are preferably set to {−ΔVo(x)+ΔVo(y)}/2.

Actually, since the voltages ±ΔVo change only from 0 to ±20 volts, theobjective lens 1212 can be settled at a high speed, specifically, in 10microseconds. As such, only 150 microseconds were required to acquirethe graphs A and B in FIG. 25( a).

Alternatively, such a large number of measurements need not be performedfor measuring the curves A, B. As shown in FIG. 25( a), a rising widthmay be measured by setting −ΔV(1), +ΔV(2), +ΔV(3) as the values of ±ΔVoto derive the graphs A, B through hyperbolic approximation to findminimum values +ΔVo(y), −ΔVo(x) for the rising. In this case, themeasurement can be made on the order of 45 microseconds.

A, B in FIG. 25( a) have the shape of hyperbola. Assuming that therising width is p (mm), and objective lens voltages ±ΔVo are q (volts),the curves A, B can be expressed by:

(p ² /a ²)−(q−c)² /b ²=1

where a, b and c are constants. Therefore, substituting three values q₁,q₂, q₃ for q and values p₁, p₂, p₃ corresponding thereto into the aboveequation, the following three equations are derived:

(p ₁ ² /a ²)−(q ₁ −c)² /b ²=1  (1)

(p ₂ ² /a ²)−(q ₂ −c)² /b ²=1  (2)

(p ₃ ² /a ²)−(q ₃ −c)² /b ²=1  (3)

The values of a, b, c are calculated from these equations (1)-(3), wherethey have minimum values when q=c. In other words, the voltage −ΔVo(x)at the objective lens which results in a minimum rising width can befound from three lens conditions. Completely in a similar manner,+ΔVo(y) can be found.

As in the graphs A, B in FIG. 25( a), the rising width is generallydifferent when a pattern edge is scanned in a first direction and whenit is scanned in a second direction. In such a case, for example, avoltage applied to the octpole astigmatism correcting lens 1205 must beadjusted to correct the astigmatism so as to further reduce the risingof the electric signal from the secondary electron beam detector 1215when the pattern edge is scanned in the first direction and in thesecond direction perpendicular thereto.

As described above, electron beam scanning/detection systems (not shown)similar in configuration to the electron beam scanning/detection system1220 are arranged in parallel with the electron beam scanning/detectionsystem 1220 such that the mutual distance is equal to an integermultiple of the dimension of one chip on the sample 1214, and thefocusing operation must be performed such that the primary electron beamis focused on the sample 1214 in each of the electron beamscanning/detection systems. However, such focusing can be substantiallysimultaneously performed, so that the throughput budget is merely aslight value.

Since this method attempts to satisfy the focusing condition not with anoptical Z sensor but with an electron-optical means, this method canadvantageously satisfy the correct focusing condition even if a sampleis charged.

As described above, the focusing operation is performed in the electronbeam scanning/detection system before a transition to a process forevaluating the sample 1214.

When a defect testing apparatus using the sixth embodiment of thepresent invention is used in the testing process (G) in the devicemanufacturing method described with reference to FIGS. 3 and 4( a),4(b), semiconductor devices even having miniature patterns can be testedat a high throughput, so that a total inspection can also be conducted,thereby making it possible to improve the yield rate of products andprevent defective products from being shipped. In this regard, thedescription related to FIG. 3 and FIGS. 4( a), 4(b) is incorporatedherewith by reference and is omitted herein.

Embodiment Relating to Anti-Vibration Apparatus Seventh Embodiment

A seventh embodiment of the present invention relates to an electronicbeam apparatus which irradiates a target position on an object with anelectronic beam to perform at least one of working, manufacturing,observation and testing for the object, and more particularly, to anelectronic beam apparatus which reduces unwanted mechanical vibrationsoccurring in a mechanical construction for aligning an electron beam, amethod of reducing vibrations, and a semiconductor manufacturing processwhich comprises a step of performing at least one of working,manufacturing, observation and testing for semiconductor devices usingthe apparatus.

Generally, an electron beam based approach for observing amicro-structure of an object employs a testing apparatus for testing fordefects on patterns formed on a wafer or the like, a scanning electronicmicroscope (SEM) and so on. However, due to its observation resolutionranging from μm to several tens of nm, observation must be made afterexternal vibrations are sufficiently removed. Also, in an apparatuswhich uses an electron beam for exposure, a vibration isolator should beused to sufficiently remove external vibrations, and the rigidity mustbe enhanced to minimize stagger due to mechanical resonance caused bythe structure of a barrel section, in order to deflect an electron beamto precisely irradiate the beam to a target position. To enhance therigidity of a construction, a reduction in size is not compatible withan enhanced rigidity due to physical constraints on dimensionsassociated with the electron-optical system, so that the rigidity isoften enhanced by increasing the thickness of the wall of the barrelportion, increasing the size of the same, and so on. However, theenhancement in rigidity by this method experiences quite a fewdisadvantages including an economical aspect, such as a limited freedomin the design including an increase in the weight of the apparatus,limitations on the shape, larger size of vibration isolation stand.

In view of the foregoing fact, the seventh embodiment of the presentinvention provides an electron beam apparatus which can appropriatelyattenuate unwanted vibrations due to the resonance of a mechanicalconstruction for aligning a beam so as to highly accurately maintain analigned beam, without necessarily enhancing the rigidity of themechanical construction, to realize mitigation of constraints indesigning, reduction in size and weight of the apparatus, and improvedeconomy, as well as a semiconductor manufacturing process which uses theapparatus in a semiconductor device manufacturing step to enableefficient manufacturing, testing, working, observation, and so on.

FIG. 26 illustrates the configuration of the seventh embodiment of thepresent invention when it is applied to an electron beam testingapparatus for testing a semiconductor wafer for defects using electronbeams. The electron beam testing apparatus 1301 illustrated in FIG. 26is of a so-called projection type, and has a mechanical constructioncomprised of an A block and a B block projecting diagonally upward fromthe A block. A primary electron beam irradiating means is arranged inthe B block for irradiating a primary electron beam, while a projectionoptical system for projecting a secondary electron beam, and an imagingmeans for detecting the intensity of the secondary electron beam areincluded in the A block.

The A block is coupled to the lowermost fixing stand 1330.

The primary electron beam irradiating means arranged in the B blockcomprises an electron beam source 1301 a including a cathode and ananode for emitting and accelerating a primary electron beam; arectangular opening 1302 a for reshaping the primary electron beam intoa rectangle; and a quadrupole lens 1302 b for reducing and focusing theprimary electron beam. Disposed below the A block are an ExB deflector1306 for deflecting the reduced primary electron beam such that itsubstantially perpendicularly impinges on a semiconductor wafer 1305 ina field in which an electric field E is orthogonal to a magnetic fieldB; a numerical aperture (NA) 1307; and an objective lens 1308 forfocusing the primary electron beam passing through the numericalaperture on the wafer 1305.

Here, the primary electron beam reduced by the quadrupole lens 1302 bforms an image of 500 μm×250 μm, for example, on a deflection mainsurface of the ExB deflector 1306, and simultaneously forms a crossoverimage of the electron beam source 1301 a on the numerical aperture 1307such that the Koehler's illumination condition is satisfied. Theobjective lens 1308 causes an image of 100 μm×50 μm, for example, to beformed on the wafer 1305, and this region is illuminated.

The wafer 1305 is placed within a sample chamber, not shown, which canbe evacuated to vacuum, and carried on a stage 1304 which is movable inan X-Y horizontal plane. Here, the relationship between the A block andB block and an XYZ orthogonal coordinate system is shown in FIG. 27( a).The surface of the wafer lies on an X-Y horizontal plane, and the Z-axisis substantially parallel to the optical axis of the projection opticalsystem. As the stage 1304 having the wafer 1305 carried thereon is movedin the X-Y horizontal plane, a surface under testing of the wafer 1305is sequentially scanned by the primary electron beam. The stage 1304 iscarried on the fixing stand 1330.

The projection optical system disposed above the A block comprises anintermediate electrostatic lens 1309, a projection electrostatic lens1311, and a diaphragm 1310 positioned between these lenses. A secondaryelectron beam emitted from the wafer 1305 due to the irradiation withthe primary electron beam, a reflected electron beam, and a scatteredelectron beam are enlarged and projected by this projection opticalsystem at a predetermined magnification (for example, 200-300 times),and focused on a lower surface of a multi-channel plate 1321, laterdescribed.

The imaging means placed at the top of the A block comprises themulti-channel plate 1321, a fluorescent screen 1322, a relay lens 1323,and an imager unit 1324. The multi-channel plate 1321 comprises a largenumber of channels in the plate for generating a larger number ofelectron beams when the secondary electron beam focused by theelectrostatic lenses 1309 and 1311 passes through the channels. In otherwords, the secondary electron beam is amplified. The fluorescent screen1322 is illuminated by the amplified secondary electron beam to generatefluorescent light of intensity corresponding to the intensity of thesecondary electron beam. In other words, the intensity of the secondaryelectron beam is transduced into the intensity of light. The relay lens1323 is positioned to introduce the fluorescent light to the imager unit1324. The imager unit 1324 is comprised of a large number of CCD imagerdevices for transducing the light introduced by the relay lens 1323 intoelectric signals. A so-called TDI (Time Delay Integral) detector ispreferably used in order to improve the S/N ratio of detected signals.While the irradiation with the primary electron beam causes thegeneration of scattered electron beam and reflected electron beam aswell as the secondary electron beam, these electron beams arecollectively called the “secondary electron beam” here.

A column 1346 comprised of the mechanical construction of the A blockand the B block coupled thereto, generally has one or more fundamentalvibration modes. A resonant frequency and resonance direction in eachfundamental vibration mode are determined by the shape, massdistribution, size, placement of machines inside the construction, andso on. For example, as illustrated in FIG. 27( b), the column 1346 hasat least mode 1 of fundamental vibration 1388. In this mode 1, thecolumn 1346 vibrates at frequency of 150 Hz, for example, substantiallyalong the Y-direction. An example of transfer function for the barrel inthis event is shown in FIG. 29. In FIG. 29, the horizontal axisrepresents the frequency, and the vertical axis represents a logarithmicvibration amplitude A. With this transfer function, the barrel has again of resonance magnification 30 dB (approximately 30 times) atresonant frequency of 150 Hz. Therefore, even with small vibrationsapplied from the outside, if the vibrations include a frequencycomponent near 150 Hz, this frequency component is amplifiedapproximately by a factor of 30 in this example to vibrate the barrel.This results in harmful events such as a blurred image.

In the prior art, for preventing this, large scaled countermeasures havebeen taken, such as the entire barrel carried on an vibration isolationstand to prevent vibrations from the outside, and/or reviewing thethickness and structure of the barrel to reduce a resonancemagnification.

In the seventh embodiment of the present invention, to avoid this, anactuator 1325 is installed on the base of the A block for applyingpressure vibrations 1390 to the barrel to cancel vibrations 1388, asillustrated in FIG. 27( c). This actuator 1325 is electrically connectedto a vibration attenuating circuit 1327, as illustrated in FIG. 28.

FIG. 28 illustrates the general configuration of the actuator 1325 andthe vibration attenuating circuit 1327. As illustrated in FIG. 28, theactuator 1325 has a piezoelectric element 1350 comprised of a dielectricmaterial 1351 having a piezoelectric effect sandwiched by electrodes1352 a and 1352 b; and a supporting stand 1354 fixed on the fixing stand1330 for supporting the piezoelectric element 1350 from the electrode1352 b side. The piezoelectric element 1350 is sandwiched between the Ablock of the barrel 1346 and the supporting stand 1354, and theelectrode 1352 a is bonded to the outer wall of the A block, while theelectrode 1352 b to the supporting stand 1354. In this way, thepiezoelectric element 1350 receives a positive pressure when the barrel1346 comes closer by reciprocal vibrations 1388, and a negative pressurewhen the barrel 1346 goes away. The piezoelectric element 1350 isinstalled at a position which is effective in suppressing the vibrations1388 of the barrel 1346. For example, it is preferably installed suchthat the directions of the vibration 1388 are orthogonal to theelectrodes 1352 a and 1352 b.

The vibration attenuating circuit 1327 comprises a variable inductance1358 and a resistor 1356 connected in series between both electrodes1352 a, 1352 b of the piezoelectric element 1350. Since the variableinductance 1358 has an inductance L, the resistor 1356 has a resistancevalue R_(D), and the piezoelectric element 1350 has an electriccapacitance C, the serially connected piezoelectric element 1350 andvibration attenuating circuit 1327 are equivalent to a series resonantcircuit designated by reference numeral 1360. The resonant frequency fo′of this series resonant circuit is expressed by:

fo′=1/{2π(LC)^(1/2)}

In the present invention, respective parameters are set such that theresonant frequency f₀′ of the resonant circuit is substantially equal tothe resonant frequency f₀ of the barrel 1346. Specifically, theinductance L of the variable inductance 1358 is tuned to establish:

fo=1/{2π(LC)^(1/2)}

for the electric capacitance C of the given piezoelectric element 1350.Actually, the capacitance C of the piezoelectric element 1350 is smallfor forming a resonant circuit to have the same mechanical resonantfrequency, so that a very large inductance L is often required, in whichcase, however, a resonant circuit can be realized by using anoperational amplifier or the like to form an equivalently largeinductance.

Also, the value R_(D) of the resistor 1356 is selected such that the Qvalue of a resonant frequency component of the series resonant circuitsubstantially matches the Q value of a resonant component having a peakin the transfer function shown in FIG. 29. The series resonant circuit1360 thus created has electric frequency characteristics designated byreference numeral 1384 in FIG. 29.

The electron beam testing apparatus 1301 illustrated in FIG. 26 iscontrolled and managed by a controller 1316. As illustrated in FIG. 26,the controller 1316 may comprise a general-purpose personal computer orthe like. This computer comprises a controller body 1314 for executing avariety of control and operational processing in accordance withpredetermined programs; a CRT 1315 for displaying results of processingby the body 1314; and an input device 1318 such as a keyboard and amouse for the operator to enter instructions. Of course, the controller1316 may be built by hardware dedicated to the electron beam testingapparatus, a workstation, or the like.

The controller body 1314 comprises a CPU, RAM, ROM, a hard disk, all notshown, a variety of control boards such as a video board, and so on. Ona memory such as RAM and hard disk, a secondary electron beam imagestorage region 1320 is allocated for storing an electric signal receivedfrom the imager unit 1324, i.e., digital image data representing asecondary electron beam image of the wafer 1305. Also, on the hard disk,a reference image storage 1313 exists for previously storing referenceimage data of the wafer which is free from defects. Further, the harddisk stores a defect detecting program 1319 in addition to a controlprogram for controlling the overall electron beam testing apparatus.This defect detecting program 1319 has functions of controllingmovements of the stage 1304 in the XY plane, performing a variety ofoperational processing such as addition for digital image data receivedfrom the imager unit 1324 in the meantime, and reproducing a secondaryelectron beam image on the storage region 1320 from the resulting data.Further, this defect detecting program 1319 reads secondary electronbeam image data created on the storage region 1320, and automaticallydetects defects on the wafer 1305 in accordance with a predeterminedalgorithm based on the image data.

Next, the action of this embodiment will be described. A primaryelectron beam is emitted from the electron beam source 1301 a, and isirradiated to the surface of the set wafer 1305 through the rectangularopening 1302 a, quadrupole lens 1302 b, ExB deflector 1306 and objectivelens 1308. As described above, a region under testing over 100 μm×50 μmis illuminated on the wafer 1305 from which a secondary electron beam isemitted. This secondary electron beam is enlarged by the intermediateelectrostatic lens 1309, the projection electrostatic lens 1311 andprojected onto the lower surface of the multi-channel plate 1321, andimaged by the imager unit 1324 to capture a secondary electron beamimage of the projected region on the wafer 1305. The stage 1304 isdriven to sequentially move the wafer 1305 every predetermined width inX-Y horizontal plane, and the foregoing procedure is executed to capturean image of the whole surface under testing.

While the enlarged secondary electron beam image is being imaged, if thebarrel 1346 is applied with an external force including a vibrationcomponent at the resonant frequency fo (150 Hz), the barrel 1346amplifies this vibration component at a resonant magnification (30 dB)determined by its transfer function to produced proper vibrations. Thevibrations 1388 apply the piezoelectric element 1350 with positive andnegative pressures. The piezoelectric element 1350 once transducesvibration energy of the barrel 1346 into electric energy which isoutput. Since both electrodes 1352 a, 1352 b of the piezoelectricelement 1350 are connected to the inductance 1358 (L) and the resistor1356 (R_(D)) in series to form a resonant circuit, the capacitiveimpedance of the piezoelectric element 1350 and the inductive impedanceL of the inductance 1358 cancel each other at the resonant frequency f₀,so that the impedance of the resonant circuit virtually has only theresistor 2056 (R_(D)). Therefore, during resonance, the electric energyoutput from the piezoelectric element 1350 is substantially fullyconsumed by the resistor 1356 (R_(D)).

Consequently, the piezoelectric element 1350 generates a force to cancelan external force applied to the piezoelectric element 1350 from thebarrel 1346, thereby making it possible to cancel the vibrations 1388generated by mechanical resonance and reduce the resonant magnification.Since the secondary electron beam is enlarged and mapped, fluctuationsin the map due to the vibration are further increased. However, thisembodiment can obviate a blurred map caused by such fluctuations.

As shown in FIG. 30, a resonant component in the transfer function 1382of the barrel 1346 as a mechanical construction (corresponding to FIG.29) is canceled by the resonant component of the series resonant circuit1360 having the electric frequency characteristic 1384, so that thebarrel 1346 has an aggregate transfer function 1386 which is low inresonant magnification as a whole.

As described above, as a satisfactory secondary electron beam image freefrom blurred image is provided, the electron beam testing apparatus 1301of this embodiment performs processing for testing the wafer 1305 fordefects from the image. As this defect testing processing, a so-calledpattern matching method or the like may be used. This method matches areference image read from the reference image storage 1313 with anactually detected secondary electron beam image to calculate a distancevalue indicative of the similarity of both. When this distance value issmaller than a predetermined threshold, the testing apparatus 1301determines “non-defective” as the similarity is high. On the other hand,when the distance value is equal to or larger than the predeterminedthreshold value, the testing apparatus 1301 determines “defective” asthe similarity is low. When determining “defective,” the testingapparatus 1301 may display a warning to the operator. In this event, theCRT 1315 may display the secondary electron beam image 1317 on itsdisplay screen. In addition, the pattern matching method may be used foreach fractional region of the secondary electron beam image.

Other than the pattern matching method, there are defect testingmethods, for example, as illustrated in FIGS. 31( a)-31(c). FIG. 31( a)illustrates an image 1331 of the first detected die, and an image of1332 of another die which is detected second time. If an image ofanother die, detected third time, is determined to be identical orsimilar to the first image 1331, a portion 1333 in the second die image1332 is determined to have a defect, so that the defective portion canbe detected.

FIG. 31( b) illustrates an example of measuring a line width of apattern formed on a wafer. 1336 designates a signal indicative of theintensity of an actual secondary electron beam when an actual pattern1334 on a wafer is scanned in a direction 1335. The width 1338 of aportion of this signal which continuously exceeds a previouslycalibrated and determined threshold level 1337 can be measured as a linewidth of the pattern 1334. If the thus measured line width is not withina predetermined range, this pattern can be determined to have a defect.

FIG. 31( c) illustrates an example of measuring a potential contrast fora pattern formed on a wafer. In the configuration illustrated in FIG.26, axially symmetric electrodes 1339 are disposed above the wafer 1305,and are applied, for example, with a potential of −10 V with respect tothe potential on the wafer at 0 V. An equi-potential plane at −2 V inthis event is shaped as indicated by 1340. Assume herein that patterns1341 and 1342 formed on the wafer are at potentials of −4 V and 0 V,respectively. In this event, since a secondary electron beam emittedfrom the pattern 1341 has an upward speed corresponding to motion energyof 2 eV on the −2 equi-potential plane 1340, so that the secondaryelectron beam jumps over a potential barrier 1340, escapes from theelectrode 1339 as indicated by a trajectory 1343, and detected by thedetector. On the other hand, a secondary electron beam emitted from thepattern 1342 cannot jump over the potential barrier of −2 V, and isdriven back to the surface of the wafer, as indicated by a trajectory1344, so that it is not detected. Therefore, an image of the detectedpattern 1341 is bright, while an image of the detected pattern 1342 isdark. Consequently, the potential contrast is can be obtained. If thebrightness of a detected image and potential are previously calibrated,the potential of a pattern can be measured from a detected image. Then,a defected portion on a pattern can be evaluated from this potentialdistribution.

As described above, the testing for defects can be realized at a higheraccuracy by making respective measurements as described above for asatisfactory secondary electron beam image free from blurred image,captured by the seventh embodiment of the present invention.

When the electron beam testing apparatus so far described as the seventhembodiment of the present invention is used in the wafer testing process(G) in the device manufacturing method described with reference to FIGS.3 and 4( a), 4(b), highly accurate testing can be efficiently made sincedetected images can be obviated from deterioration due to vibrations ofthe mechanical construction, making it possible to prevent defectiveproducts from being shipped. In this regard, the description related toFIG. 3 and FIGS. 4( a), 4(b) is incorporated herewith by reference andis omitted herein.

The seventh embodiment of the present invention is not limited to theforegoing, but may be arbitrarily modified in a preferred manner withinthe gist of the present invention. For example, the mechanical resonantfrequency and mode are not necessarily single, but generally, aplurality of resonant frequencies and modes occur, in which case arequired number of actuators 1325 may be installed at required locationsof the barrel to support them. For example, when the mechanicalconstruction block A illustrated in FIG. 27( b) has vibrations in theX-direction as well as the vibrations 1388 in the Y-direction, anotheractuator may be installed to cancel the vibrations in the X-direction.Further, when the B block and D block also have independent propervibrations, actuators may be installed for these blocks as well.

The vibration attenuating circuit 1327 need not be equivalent to theseries resonant circuit 1360, but may be implemented by a circuit, theelectric frequency characteristics of which have a plurality of resonantfrequencies when the mechanical proper vibrations have a plurality ofresonant frequencies in the same vibration direction.

The actuator may be installed not only in the barrel, but also in a partrequired to precisely align the beam position, for example, the X-Ystate 1304, or in optics of a variety of optical devices.

While the semiconductor wafer 1305 has been taken as an example of asample under testing for the electron beam testing apparatus of theseventh embodiment, the sample under testing is not limited to this, butarbitrary one may be selected as long as defects thereon can be detectedby electron beams. For example, a mask formed with an exposure patternfor a wafer may be chosen as an object under testing.

Further, the seventh embodiment can be applied to the entirety ofapparatuses which apply electron beams for irradiate a beam to a targetposition on an object. In this event, the seventh embodiment can beextended not only to the testing of the object but also to an apparatuswhich performs at least some of working, manufacturing and observationthereof. Of course, the concept of the object herein referred toencompasses not only the wafer and mask as mentioned, but also anarbitrary object for which at least some of testing, working,manufacturing and observation thereof can be conducted with the beam.The device manufacturing method may also be applied not only to thetesting during a semiconductor device manufacturing step but also to aprocess itself for manufacturing semiconductor devices with beams.

While the configuration illustrated in FIG. 26 has been shown as anelectron beam testing apparatus of the seventh embodiment, theelectron-optical system and so on can be arbitrarily modified asrequired. For example, while the electron beam irradiating means of theelectron beam testing apparatus 1301 is the type that directs theprimary electron beam vertically to the surface of the wafer 1305 fromabove, the ExB deflector 1306 may be omitted such that the primaryelectron beam is directed diagonally into the surface of the wafer 1305.

Embodiment Relating to Holding of Wafer Eighth Embodiment

An eighth embodiment of the present invention relates to anelectrostatic chuck for electrostatically sucking and holding a wafer inan electron beam apparatus, a combination of the wafer and theelectrostatic shuck, particularly, a combination of an electrostaticchuck usable in an electron beam apparatus using decelerating electricfield objective lenses, and a wafer, and a device manufacturing methodwhich uses an electron beam apparatus that comprises a combination of anelectrostatic chuck and a wafer.

A known electrostatic chuck for electrostatically chucking and fixing awafer comprises electrode layers disposed on a substrate, formed of aplurality of electrodes insulated from each other, and a power supplyfor sequentially applying a voltage from one electrode to another. Also,an electron beam apparatus using decelerating electric field objectivelens is known.

For evaluating a wafer in the middle of a process with an electron beamapparatus using decelerating electric field objective lens, it isnecessary to apply a negative high voltage to the wafer. In this event,sudden application of a high negative voltage would break devices in themiddle of the process, so that the voltage must be gradually applied.

On the other hand, a majority of wafers are coated with an insulatingfilm such as SiO₂, a nitride film or the like on side surfaces and backsurfaces, so that when a zero potential or a low potential is to beapplied to the wafer, no voltage is applied to the wafer. Further,although a wafer centrally bowed in convex toward the electrostaticchuck can be relatively easily chucked and fixed, a wafer centrallybowed in concave toward the chuck presents a problem that, with asingle-pole electrostatic chuck, only a peripheral portion is chuckedbut a central portion is held unchucked.

The eighth embodiment of the present invention, for solving the aboveproblems, provides an electrostatic chuck for use with deceleratingelectric field objective lens, which is capable of chucking a wafercoated with an insulating film on its side surface and back surface andcentrally bowed in concave toward the chuck, a combination of a waferand an electrostatic chuck, and a device manufacturing method forevaluating a wafer in the middle of a process using such a combinationof an electrostatic chuck and a wafer.

FIG. 32 is a plan view of an electrostatic chuck 1410 in the eighthembodiment of the present invention, removing a wafer to show anelectrode plate 1412. FIG. 33 is a schematic cross-sectional view in thevertical direction along a line M-M of the electrostatic chuck of FIG.32, showing that a wafer is carried but not applied with a voltage. Theelectrostatic chuck 1410 has a laminate structure comprised of asubstrate 1405, an electrode plate 1412 and an insulating layer 1404, asillustrated in FIG. 33. The electrode plate 1412 includes a firstelectrode 1401 and a second electrode 1402. The first electrode 1401 andsecond electrode 1402 are separated such that they can be separatelyapplied with voltages, and are formed of thin films such that they canbe moved at a high speed without generating eddy currents in a magneticfield.

The first electrode 1401 is comprised of a central portion and some of aperipheral portion of the circular electrode plate 1412 on the planview, while the second electrode 1402 is comprised of the remaininghorseshoe-shaped peripheral portion. The insulating layer 1404 isdisposed on the electrode plate 1412. The insulating layer 1404 isformed of a sapphire substrate of 1 mm in thickness. Sapphire is singlecrystal of alumina and has a high breakdown voltage since it iscompletely free of bore as in alumina ceramics. For example, a sapphiresubstrate of 1 mm in thickness can sufficiently withstand a potentialdifference of 10⁴ V or higher.

The wafer 1403 is applied with a voltage through contacts 1406 having aknife-edge shaped metal portion. As illustrated in FIG. 33, two contacts1406 are brought into contact with the side surface of the wafer 1403.The two contacts 1406 are used in order to avoid a possible failure ofconduction and a force generated to urge the wafer 1403 to one side, ascould be otherwise experienced if only one contact was used. Theinsulating layer 1404 is broken for making the conduction. However,since particles could be scattered upon discharging, the contacts 1406are connected to a power supply 1416 through a resistor 1414 to preventa large discharge from occurring. Since this resistor 1414 prevents theformation of a conduction hole if it is too large, and causes a largedischarge to scatter particles if it is too small, an allowable valuefor the resistor is determined for each insulating layer 1404.

FIG. 34( a) shows a time chart of applied voltages. The first electrodeis applied with 4 kV at time t=0, as indicated by a line A. At timet=t₀, at which the wafer is chucked both in the central portion and inthe peripheral portion, the second electrode is applied with 4 kV, asindicated by a line B. At time t=t₁, a voltage C across the wafer iscontrolled to be gradually deepened (lowered) to reach −4 kV at timet=t₂. The first electrode and the second electrode are applied withgradually reduced voltages from time t=t₁ to time t=t₂, and with 0 V att=t₂.

At time t=t₃ at which evaluation has been made for the wafer chucked andheld by the chuck, the voltage C across the wafer is reduced to 0 V, andthe wafer is removed to the outside.

When the electrostatic chuck holds a wafer with a potential differenceof 2 kV, rather than a potential difference of 4 kV, the first electrodeand the second electrode are applied with voltages A′, B′ at 2 kV,respectively, as indicated by one-dot chain lines in FIG. 34. When thewafer is applied with −4 kV, the first electrode and the secondelectrode are applied with −2 kV, respectively. In this way, theinsulating layer 2104 is prevented from being applied with a voltagemore than necessity, by the application of voltages, so that theinsulating layer can be prevented from breakdown.

FIG. 35 is a block diagram illustrating an electron beam apparatus whichcomprises the electrostatic chuck described above. Unnecessary beams areremoved from electron beams emitted from an electron beam source 1431 byan aperture of an anode 1432 which determine the numerical aperture(NA). The electron beam is reduced by a condenser lens 1437 and anobjective lens 1443, and focused on a wafer 1403 applied with −4 kV, andscans on the wafer 1403 with deflectors 1438 and 1442. A secondaryelectron beam emitted from the wafer 1403 is collected by the objectivelens 1443, deflected to the right by approximately 35° by an ExBseparator 1442, and detected by a secondary electron beam detector 1440to capture an SEM image on the wafer. In the electron beam apparatus ofFIG. 35, reference numerals 1433, 1435 designate alignment tools; 1434an astigmatism correcting tool; 1436 an opening plate; 1441 a shield;and 1444 an electrode. The electrostatic chuck described in FIGS. 33 and34 is disposed below the wafer 1403.

When the eighth embodiment of the present invention is used in thetesting process (G) in the device manufacturing method described withreference to FIGS. 3 and 4( a), 4(b), semiconductor devices even havingminiature patterns can be tested at a high throughput, so that a totalinspection can also be conducted, thereby making it possible to improvethe yield rate of products and prevent defective products from beingshipped. In this regard, the description related to FIG. 3 and FIGS. 4(a), 4(b) is incorporated herewith by reference and is omitted herein.

The manner of increasing or decreasing the voltages applied to theelectrostatic chuck is not limited to that shown in FIG. 34. Forexample, as shown in FIG. 34( b), an exponentially changing voltage mayalso be used. In essence, any voltage may be used as long as it reachesa predetermined voltage without delay.

Embodiment Relating to Stage for Carrying Sample Ninth Embodiment

A ninth embodiment of the present invention relates to an apparatus forirradiating an electron beam to a sample carried on an XY stage, adefect testing apparatus or an exposure apparatus utilizing theapparatus, and a device manufacturing method using these apparatuses.

A stage for accurately positioning a sample in a vacuum is used in anapparatus which irradiates an electron beam to the surface of a samplesuch as a semiconductor wafer, or the like to expose the surface of thewafer with a pattern such as a semiconductor circuit or to test patternsformed on the surface of the sample, or in an apparatus which irradiatesan electron beam to perform ultra-precision working on the sample.

When highly accurate positioning is required to such a stage, astructure of supporting a stage with static pressure bearings in anon-contact manner is employed. In this event, a degree of vacuum ismaintained in a vacuum chamber by forming a differential pumpingmechanism for exhausting a high pressure gas in a range of thehydorstatic pressure bearing such that the high pressure gas suppliedfrom the static pressure bearings will not be exhausted directly to thevacuum chamber.

An example of such a stage according to the prior art is illustrated inFIG. 36. In the structure of FIG. 36, a leading end of a barrel 1501 ofan electron beam apparatus for generating an electron beam forirradiating a sample, i.e., an electron beam irradiating tip 1502 isattached to a housing 1508 which constitutes a vacuum chamber C. Theinside of the barrel is evacuated to vacuum by a vacuum pipe 1510, andthe chamber C is evacuated to a vacuum by a vacuum pipe 1511. Then,electron beam is irradiated from the leading end 1502 of the barrel 1501to a sample S such as a wafer placed therebelow.

The sample S is removably held on a sample base 1504 in a known method.The sample base 1504 is mounted on the top surface of a Y-directionmovable section 1505 of an XY stage (hereinafter simply called the“stage”) 1503. The Y-direction movable section 1505 has a plurality ofstatic pressure bearings 1509 attached on surfaces (both left and rightside surfaces and a lower surface in FIG. 36[A]) opposite to a guidesurface 1506 a of an X-direction movable section 1506 of the stage 1503.The Y-direction movable section is movable in the Y-direction (in theleft-to-right direction in FIG. 36[B]) while maintaining a small gapbetween the guide surface and the opposite surfaces by the action of thestatic pressure bearings 1509. Further, around the hydrostatic pressurebearings, a differential pumping mechanism is disposed to prevent a highpressure gas supplied to the static pressure bearings from leaking intothe inside of the vacuum chamber C. This situation is shown in FIG. 37.Double grooves 1518 and 1517 are formed around the static pressurebearings 1509, and these grooves are evacuated to vacuum at all times bya vacuum pipe and a vacuum pump, not shown. With such a structure, theY-direction movable section 1505 is supported in a non-contact state invacuum so that it is freely movable in the Y-direction. These doublegrooves 1518 and 1517 are formed to surround the static pressurebearings 1509 of the movable section 1505 on the surface on which thestatic pressure bearings are disposed. Since the static pressure bearingmay have a known structure, detailed description thereon is omitted.

The X-section movable section 1506, which carries the Y-directionmovable section 1505 has a concave shape open to above, as is apparentfrom FIG. 36. The X-direction movable section 1506 is also provided withcompletely similar hydrostatic pressure bearings and grooves, such thatthe X-direction movable section 1506 is supported to a stage stand 1507in a non-contact manner, and is freely movable in the X-direction.

By combining movements of these Y-direction movable section 1505 andX-direction movable section 1506, it is possible to move the sample S toan arbitrary position in the horizontal direction with respect to theleading end of the barrel, i.e., the electron beam irradiating tip 1502to irradiate electron beams to a desired position of the sample.

In the stage having a combination of the static pressure bearings andthe differential pumping mechanism, the guide surfaces 1506 a and 1507 aopposing the static pressure bearings 1509 reciprocate between a highpressure gas atmosphere of the static pressure bearings and a vacuumenvironment within the chamber as the stage is moved. In this event,while the guide surfaces are exposed to the high pressure gasatmosphere, the gas is adsorbed to the guide surfaces, and the adsorbedgas is released as the guide surfaces are exposed to the vacuumenvironment. Such states are repeated. Therefore, as the stage is moved,the degree of vacuum within the chamber C is degraded, giving rise to aproblem that the aforementioned processing such as exposure, testing andworking, by use of the electron beam cannot be stably performed and thatthe sample is contaminated.

To solve such problem, the ninth embodiment of the present inventionprovides:

an electron beam apparatus which prevents the degree of vacuum fromdegrading to permit stable processing such as testing and working by useof an electron beam;

an electron beam apparatus which has a non-contact supporting mechanismby means of static pressure bearings and a vacuum sealing mechanism bymeans of differential pumping to generate a pressure difference betweenan electron beam irradiation region and a supporter of the staticpressure bearings;

an electron beam apparatus for reducing a gas released from the surfaceof parts facing the static pressure bearings;

a defect testing apparatus using the electron beam apparatus to test thesurface of a sample, or an exposure apparatus for delineating patternson the surface of the sample; and

a semiconductor manufacturing method for manufacturing semiconductordevices using the electron beam apparatus as described above.

In the following, the ninth embodiment of the present invention will bedescribed with reference to the drawings. In FIG. 38, a partition plate1514 largely extending substantially horizontally in the +Y directionand in the −Y direction (in the left and right directions in FIG. 38[B])is attached on the top surface of a Y-direction movable section 1505 ofa stage 1503, such that a reducer 1550 having a small conductance isformed at all times between the top surface of the X-direction movablesection 1506 and the partition plate 1514. Also, on the top surface ofan X-direction movable section 6, a similar partition plate 1512 isplaced to extend in the ±X-directions (in the left and right directionsin FIG. 38[A]), such that a reducer 1551 is formed at all time betweenthe top surface of a stage stand 1507 and the partition plate 1512. Thestage stand 1507 is fixed on a bottom wall in a housing 1508 in a knownmanner.

Thus, the reducers 1550 and 1551 are formed at all times when the samplebase 1504 is moved to whichever position, so that even if a gas isreleased from the guide surfaces 1506 a and 1507 a while the movablesections 1505 and 1506 are moved, the movement of the released gas isprevented by the reducers 1550 and 1551, thereby making it possible tosignificantly suppress an increase in pressure in a space 1524 near thesample irradiated with electron beams.

The side surface and the lower surface of the movable section 1505 andthe lower surface of the movable section 1506 of the stage are formedwith grooves around the static pressure bearings 1509 for differentialpumping, as illustrated in FIG. 37. Since evacuation to vacuum isperformed through these grooves, the released gas from the guidesurfaces are mainly exhausted by these differential pumping unit whenthe reducers 1550, 1551 are formed. Therefore, the pressures in thespaces 1513 and 1515 within the stage are higher than the pressurewithin the chamber C. Therefore, if locations which are evacuated tovacuum are separately provided, not only the spaces 1513 and 1515 areevacuated through the differential pumping grooves 1517 and 1518, butalso the pressures in the spaces 1513 and 1515 can be reduced to furthersuppress an increase in pressure near the sample 1524. Vacuum evacuationpassages 1511-1 and 1511-2 are provided for this purpose. The evacuationpassages extend through the stage stand 1507 and the housing 1508 andcommunicate with the outside. Also, the evacuation passage 1511-2 isformed in the X-direction movable section 1506, and is open to the lowersurface of the X-direction movable section 1506.

While the provision of the partition plates 1512 and 1514 results in arequirement of increasing the size of the chamber C such that thechamber C does not interfere with the partition walls, this aspect canbe improved by making the partition plates of a retractile material orin a telescopical structure. In this embodiment, the partition wall ismade of rubber or in bellows form, and its end in the moving directionis fixed to the X-direction moving section 1506 for the partition plate1514, and to an inner wall of the housing 1508 for the partition plate1512, respectively.

FIG. 39 illustrates a first exemplary modification in the ninthembodiment of the present invention. In this example, a cylindricalpartition 1516 is formed around the leading end of the barrel, i.e., theelectron beam irradiating tip 1502 to provide a reducer between the topsurface of the sample S and the electron beam irradiating tip 1502. Insuch a configuration, even if a gas is released from the XY stage tocause an increased pressure within the chamber C, the inside 1524 of thepartition is partitioned by the partition 1516 and the gas is exhaustedthrough the vacuum pipe 1510, so that a pressure difference is producedbetween the inside of the chamber C and the inside 1524 of the partitionto suppress an increased pressure within the space 1524 in thepartition. While a gap between the partition 1516 and the surface of thesample varies depending on the pressure maintained within the chamber Cand around the irradiating tip 1502, approximately several tens of μm toseveral mm are proper. The inside of the partition 1516 is communicatedwith the vacuum pipe by a known method.

Also, some electron beam apparatus may apply a sample S with a highvoltage of approximately several kV, so that a conductive materialplaced near the sample can give rise to a discharge. In this case, thepartition 1516 may be made of an insulating material such as ceramics toprevent a discharge between the sample S and the partition 1516.

A ring member 1504-1 disposed around the sample S (wafer) is aplate-shaped adjusting part fixed to the sample base 1504, which is setat the same level as the wafer such chat a small gap 1525 is formed overthe entire periphery of the leading end of the partition 1516 even if anend portion of a sample such as a wafer is irradiated with an electronbeam. In this way, even when an electron beam is irradiated to whicheverposition of the sample S, the constant small gap 1552 is formed at alltimes at the leading end of the partition 1516, thereby making itpossible to stably maintain the pressure in the space 1524 around theleading end of the barrel.

FIG. 40 illustrates a second exemplary modification in the ninthembodiment of the present invention. A partition 1519 containing adifferential pumping structure is disposed around an electron beamirradiating tip 2 of the barrel 1501. The partition 1519 has acylindrical shape, and a circumferential groove 1520 is formed inside.An exhaust passage 1521 extends upward from the circumferential grove.The exhaust passage is connected to a vacuum pipe 1523 through aninternal space 1522. There is a small gap ranging from several tens ofμm to several mm between the lower end of the partition wall 1519 andthe upper surface of the sample S.

In such a configuration, even if a gas is released from the stage inassociation with a movement of the stage to cause an increased pressurewithin the chamber C, and the gas is going to flow into the leading end,i.e., the electron beam irradiating tip 1502, the partition 1519 reducesthe gap between the sample S and the leading end to make the conductanceextremely small, so that the gas is impeded from flowing into theelectron beam irradiating tip 1502 and the amount of flowing gas isreduced. Further, the introduced gas is exhausted from thecircumferential groove 1520 to the vacuum pipe 1523, so thatsubstantially no gas flows into the space 1524 around the electron beamirradiating tip 1502, thereby making it possible to maintain thepressure at the electron beam irradiating tip 1502 at a desired highvacuum.

FIG. 41 illustrates a third exemplary modification in the ninthembodiment of the present invention. A partition 1526 is formed aroundthe chamber C and the electron beam irradiating tip 1502 to separate theelectron beam irradiating tip 1502 from the chamber C. This partition1526 is coupled to a freezer 1530 through a supporting member 1529 madeof a high thermally conductive material such as copper and aluminum, andis cooled at −100° C. to −200° C. A member 1527 is provided forpreventing thermal conduction between the cooled partition 1526 and thebarrel, and is made of a low thermally conductive material such asceramics and resin material. Also, a member 1528, which is made of anon-insulating material such as ceramics, is formed at a lower end ofthe partition 1526 and is responsible for preventing the sample S andthe partition 1526 from discharging.

In such a configuration, gas molecules which are going to flow from thechamber C into the electron beam irradiating tip are impeded by thepartition 1526 from flowing toward the electron beam irradiating tip,and even if the molecules flow, they are frozen and trapped on thesurface of the partition 1526, thereby making it possible to maintainlow the pressure in the space 1524 in which the electron beamirradiating tip 1502 is positioned.

As the freezer, a variety of freezers can be used such as a liquidnitrogen based freezer, an He freezer, a pulse tube type freezer, and soon.

FIG. 42 illustrates a fourth exemplary modification in the ninthembodiment of the present invention. Partition plates 1512, 1514 similarto that illustrated in FIG. 38 are disposed on both movable sections ofthe stage 1503, so that even if the sample base 1504 is moved to anarbitrary position, the space 1513 within the stage and the inside ofthe chamber C are partitioned by these partitions through reducers 1550,1551. Further, a partition 1516 similar to that illustrated in FIG. 39is formed around the electron beam irradiating tip 1502 to partition theinside of the chamber C and the space 1524, in which the electron beamirradiating tip 1502 is positioned, through a reducer 1552. Therefore,even if a gas adsorbed on the stage is released into the space 1513while the stage is moved to increase the pressure in this space, anincreased pressure in the chamber C is suppressed, and an increasedpressure in the space 1524 is further suppressed. In this way, thepressure in the electron beam irradiation space 1524 can be maintainedin a low state. In addition, the space 1524 can be stably maintained ata yet lower pressure by providing the partition 1519 which contains adifferential pumping mechanism as illustrated in the partition 1516, orthe partition 1526 cooled by a freezer, as illustrated in FIG. 40.

FIG. 43 schematically illustrates an optical system and a detectionsystem of the electron beam apparatus according to the ninth embodiment.While the optical system is disposed within the barrel 1501, theseoptical system and detector are illustrative in all sense, and arbitraryoptical system and detector may be used as required. An optical system1560 of the electron beam apparatus comprises a primary optical system1561 for irradiating an electron beam to a sample S carried on the stage1503; and a secondary optical system 1571 into which a secondaryelectron beam emitted from the sample is introduced. The primary opticalsystem 1561 comprises an electron beam source 1562 for emitting anelectron beam; a lens system 1563, 1564 comprised of two-stageelectrostatic lenses for converging an electron beam emitted from theelectron beam source 1562; a deflector 1565; a Wien filter 1566 fordeflecting an electron beam such that its optical axis is orientedperpendicular to the surface of an object; and a lens system 1567, 1568comprised of two-stage electrostatic lenses. These components arepositioned in order obliquely with respect to the optical axis of theelectron beam vertical to the surface of the sample S (sample surface)with the electron beam source 1562 placed at the top, as illustrated inFIG. 36. The Wien filter 1566 comprises an electrode 1566-1 and a magnet1566-2.

The secondary optical system 1571, which is an optical system into whicha secondary electron beam emitted from the sample S is introduced,comprises a lens system 1572, 1573 comprised of two-stage electrostaticlenses disposed above the Wien filter 1566 in the primary opticalsystem. A detector 1580 detects a secondary electron beam sent throughthe secondary optical system 1571. Since the structure and function ofthe respective components in the optical system 1560 and the detector1580 are identical to conventional ones, detailed description thereon isomitted.

An electron beam emitted from the electron beam source 1562 is reshapedby a square aperture of the electron beam source, reduced by thetwo-stage lens systems 1563 and 1564, has its optical axis adjusted bythe deflector 1565, and focused on a deflection central surface of theWien filter 1566 in a square having one side of 1.25 mm. The Wien filter1566 is arranged such that an electric field and a magnetic field areorthogonal to each other in a plane perpendicular to the normal of thesample, and allows an electron beam to go straight therethrough when therelationship among the electric field, magnetic field, and energy of theelectron beam satisfies a predetermined condition, and otherwisedeflects the electron beam in a predetermined direction depending on themutual relationship among these electric field, magnetic field, andenergy of the electric field. In FIG. 43, the Wien filter is set toallow an electron beam from the electron beam source to impingeperpendicularly to the sample S, and a secondary electron beam emittedfrom the sample to go straight therethrough in the direction of thedetector 1580. The reshaped beam deflected by the Wien filter 1566 isreduced by the lens systems 1567, 1568 by a factor of five, andprojected onto the sample S. A secondary electron beam havinginformation on a pattern image emitted from the sample S is enlarged bylens systems 1567, 1568 and 1572, 1573 to form a secondary electron beamimage on the detector 1580. The four-stage enlarging lenses constitutedistortion-free lenses since the lens system 1567 and 1568 forms asymmetric tablet lens, and the lens system 1572 and 1573 also forms asymmetric tablet lens.

When the ninth embodiment of the present invention is used in thetesting process (G) or the exposure process (c) in the devicemanufacturing method described with reference to FIGS. 3 and 4( a),4(b), miniature patterns can be stably tested or exposed at a highaccuracy, thereby making it possible to improve the yield rate ofproducts and prevent defective products from being shipped. In thisregard, the description related to FIG. 3 and FIGS. 4( a), 4(b) isincorporated herewith by reference and is omitted herewith.

Embodiment Relating to Stage for Carrying Sample Tenth Embodiment

A tenth embodiment of the present invention relates to an apparatus forirradiating an electron beam to a sample carried on an XY stage, andmore particularly, to an electron beam apparatus which comprises adifferential pumping mechanism around a barrel without containing thedifferential pumping mechanism in an XY stage, a defect testingapparatus or an exposure apparatus utilizing the apparatus, and a devicemanufacturing method using these apparatuses.

As previously described with reference to FIGS. 36 and 37, aconventional XY stage which has a combination of static pressurebearings and a differential pumping mechanism, because of the inclusionof the differential pumping mechanism, is complicated in structure andlarge as compared with a static pressure bearing type stage used in theatmosphere, and also has a problem in low reliability as a stage and ahigh cost. In this embodiment, FIGS. 36, 37, and the previousdescription thereon are incorporated herewith by reference asdescription of the prior art.

The tenth embodiment of the present invention, to solve the aboveproblem, provides:

an electron beam apparatus which eliminates a differential exhaustmechanism from an XY stage to enable simplification of structure andreduction in size;

an electron beam apparatus which comprises a differential pumpingmechanism for evacuating a housing which contains the XY stage to vacuumand evacuating a region on the surface of a sample irradiated with anelectron beam;

a defect testing apparatus for testing the surface of the sample usingthe electron beam apparatus, or an exposure apparatus for drawingpatterns on the surface of the sample; and

a semiconductor manufacturing method for manufacturing semiconductordevices using the electron beam apparatus as mentioned above.

In the tenth embodiment, a term “vacuum” is used in a normal meaning inthe art.

In the following, the tenth embodiment of the present invention will bedescribed with reference to the drawings.

In FIG. 44, a leading end of a barrel 1601, i.e., an electron beamirradiating tip 1602 for irradiating an electron beam to a sample isattached to a housing 1614 which defines a vacuum chamber C. A sample Scarried on a movable table in the X-direction (in the left-to-rightdirection in FIG. 44) of an XY stage 1603 is positioned beneath thebarrel 1601. The sample S can be precisely irradiated with an electronbeam at an arbitrary position on the surface of the sample by the highlyaccurate XY stage 1603.

A pedestal 1606 of the XY stage 1603 is fixed on a bottom wall of thehousing 1614, and a Y-table 1605 movable in the Y-direction (in thedirection vertical to the sheet in FIG. 24) is carried on the pedestal1606. On both sides of the Y-table 1605 (on left and right sides in FIG.24), protrusions are formed protruding into recessed grooves of a pairof Y-direction guides 1607 a and 1607 b carried on the pedestal 1606formed in the sides facing the Y-table. The recessed grooves extend inthe Y-direction substantially over the entire length of the Y-directionguides. Static pressure bearings 1611 a, 1609 a, 1611 b, 1609 b in aknown structure are disposed on the top surface, bottom surface and sidesurfaces of the protrusions protruding into the recessed grooves,respectively. A high pressure gas is blown off through these staticpressure bearings to support the Y-table 1605 with respect to theY-direction guides 1607 a, 1607 b in a non-contact manner and to allowthe same to smoothly reciprocate in the Y-direction. Also, a linearmotor 1612 in a known structure is disposed between the pedestal 1606and the Y-table 1605 to drive the Y-table 1605 in the Y-direction bymeans of the linear motor. The Y-table is supplied with a high pressuregas through a flexible pipe 1622 for high pressure gas supply, so thatthe high pressure gas is supplied to the static pressure bearings 1609 ato 1611 a and 1609 b to 1611 b through a gas passage (not shown) formedin the Y-table. The high pressure gas supplied to the static pressurebearings blows out into a gap of several microns to several tens ofmicrons formed between opposing guiding surfaces of the Y-directionguide to serve to precisely position the Y-table with respect to theguide surfaces in the X-direction and Z-direction (upward and downwarddirections in FIG. 44).

An X-table 1604 is carried on the Y-table for movement in theX-direction (in the left-to-right direction in FIG. 44). On the Y-table1605, a pair of X-direction guides 1608 a, 1608 b (only 1608 a is shown)identical in structure to the Y-direction guides 1607 a, 1607 b for theY-table are disposed with the X-table 1604 interposed therebetween. Arecessed groove is also formed in the side of the X-direction guidefacing the X-table, and a protrusion is formed in a side portion of theX-table (a side portion facing the X-direction guide), protruding intothe recessed groove. The recessed groove extends substantially over theentire length of the X-direction guide. Static pressure bearings (notshown) similar to the static pressure bearings 1611 a, 1609 a, 1610 a,1611 b, 1609 b, 1610 b are disposed on the top surface, bottom surfaceand side surfaces of the protrusion of the X-direction table 4protruding into the recessed groove in similar positioning. Between theY-table 1605 and the X-table 1604, a linear motor 1613 in a knownstructure is disposed so that the X-table is driven in the X-directionby means of the linear motor. Then, the X-table 1604 is supplied with ahigh pressure gas through a flexible pipe 1621 to supply the highpressure gas to the static pressure bearings. The high pressure gas isblown out from the static pressure bearings to the guide surfaces of theX-direction guide to highly accurately support the X-table 1604 withrespect to the Y-direction guide in a non-contact manner. The vacuumchamber C is evacuated by vacuum pipes 1619, 1620 a, 1620 b connected toa vacuum pump or the like in a known structure. The inlet sides (withinthe vacuum chamber) of the pipes 1620 a, 1620 b extend through thepedestal 1606 and are open near a position at which the high pressuregas is exhausted from the XY stage 1603 on the top surface of thepedestal 1606, to maximally prevent the pressure within the vacuumchamber from rising due to the high pressure gas blown out from thestatic pressure bearings.

A differential exhaust mechanism 1625 is disposed around the leading endof the barrel 1601, i.e., the electron beam irradiating tip 1602, suchthat the pressure in the electron beam irradiation space 1630 is heldsufficiently low even if the pressure in the vacuum chamber C is high.Specifically, an annular member 1626 of the differential exhaustmechanism 1625 attached around the electron beam irradiating tip 1602 ispositioned with respect to the housing 1614 such that a small gap (fromseveral micron to several hundred microns) 1640 is formed between thelower surface (the surface opposing the sample S) and the sample, and anannular groove 1627 is formed on the lower surface thereof. The annulargroove 1627 is connected to a vacuum pump or the like, not shown,through an exhaust pipe 1628. Therefore, the small gap 1640 is evacuatedthrough the annular groove 1627 and an exhaust port 1628, so that evenif gas molecules attempt to invade from the vacuum chamber C into thespace 1630 surrounded by the annular member 1626, they are exhausted. Inthis way, the pressure within the electron beam irradiation space 1630can be held low to irradiate an electron beam without problem.

The annular groove may be in a double structure or in a triple structuredepending on the pressure within the chamber or the pressure within theelectron beam irradiation space 1630.

For the high pressure gas supplied to the static pressure bearings, drynitrogen is generally used. However, if possible, a highly pure inertgas is further preferable. This is because if impurities such asmoisture and oil components are included in the gas, these impuritymolecules will attach on the inner surface of the housing which definesthe vacuum chamber, and on the surfaces of components of the stage todeteriorate the degree of vacuum, and will attach on the surface of thesample to deteriorate the degree of vacuum in the electron beamirradiation space.

In the foregoing description, the sample S is not generally carrieddirectly on the X-table, but carried on a sample base which hasfunctions of removably holding the sample, and making a slightpositional change with respect to the XY stage 1603, and so on. However,since the presence or absence of the sample base, and its structure arenot related to the gist of the present invention, they are omitted forsimplifying the description.

Since the electron beam apparatus described above can use a staticpressure bearing stage mechanism used in the atmosphere as it is, ahighly accurate XY stage equivalent to a highly accurate stage foratmosphere used in an exposure apparatus and so on can be implemented inan XY stage for an electron beam apparatus substantially at the samecost and in the same size.

The structure and positioning of the static pressure guides andactuators (linear motors) described above are merely one embodiment inall sense, and any of static pressure guides and actuators can beapplied if it is usable in the atmosphere.

Next, FIG. 45 shows exemplary values for the sizes of the annular member1626 of the differential exhaust mechanism, and the annular grooveformed therein. In this example, the annular groove has a doublestructure comprised of 1627 a and 1627 b which are spaced apart in aradial direction. A flow rate of the high pressure gas supplied to thestatic pressure bearings is generally at about 20 L/min (converted tothe atmospheric pressure). Assuming that the vacuum chamber C isevacuated by a dry pump having an exhausting rate of 20000 L/min througha vacuum pipe having an inner diameter of 50 mm and a length of 2 m, thepressure in the vacuum chamber is approximately 160 Pa (approximately1.2 Torr). In this event, if the dimensions of the annular member 1626of the differential exhaust mechanism, annular groove and so on aredetermined as shown in FIG. 45, the pressure in the electron beamirradiation space 1630 can be set at 10⁻⁴ Pa (10⁻⁶ Torr).

The differential exhaust mechanism is not limited in shape to theconcentric shape as in this embodiment, but may be in a rectangular or apolygonal shape, as long as it can maintain the pressure in the electronbeam irradiation space 1630 at a predetermined pressure. In addition, itmay not be provided over the entire periphery but a portion thereof.

FIG. 46 illustrates a piping system for the apparatus illustrated inFIG. 44. The vacuum chamber C defined by the housing 1614 is connectedto a dry vacuum pump 1653 through vacuum pipes 1674, 1675. Also, theannular grove 1627 of the differential pumping mechanism 1625 isconnected to a turbo molecular pump 1651, which is an ultra-high vacuumpump, through a vacuum pipe 1670 connected to the exhaust port 1628.Further, the inside of the barrel 1601 is connected to a turbo molecularpump 1652 through a vacuum pipe 1671 connected to an exhaust port 1618.These turbo molecular pumps 1651, 1652 are connected to the dry vacuumpump 1653 through vacuum pipes 1672, 1673. (While in FIG. 46, a singledry vacuum pump is in double use for a roughing pump as the turbomolecular pump and a vacuum evacuation pump for the vacuum chamber, itis contemplated that separate dry vacuum pumps may be used forevacuation depending on the flow rate of the high pressure gas suppliedto the static pressure bearings of the XY stage, the volume and innersurface area of the vacuum chamber, and the inner diameter and length ofthe vacuum pipe.)

The static pressure bearing of the XY stage 1603 are supplied withhighly pure inert gas (N₂ gas, Ar gas or the like) through the flexiblepipes 1621, 1622. The gas molecules blown out from the static pressurebearings diffuse in the vacuum chamber, and are exhausted by the dryvacuum pump 2353 through the exhaust ports 1619, 1620 a, 1620 b. Also,the gas molecules introducing into the differential exhaust mechanismand the electron beam irradiation space are sucked from the annulargroove 1627 or the leading end of the barrel 1601, exhausted by theturbo molecular pumps 1651 and 1652 through the exhaust ports 1628 and1618, and exhausted by the dry vacuum pump 1653 after they have beenexhausted by the turbo molecular pump.

In this way, the highly pure inert gas supplied to the static pressurebearings is collected and exhausted by the dry vacuum pump.

On the other hand, the dry vacuum pump 1653 has an exhaust portconnected to a compressor 1654 through a pipe 1676, while the compressor2316 has an exhaust port connected to the flexible pipes 1621, 1622through pipes 1677, 1678, 1679 and regulators 1661, 1662. Therefore, thehighly pure inert gas exhausted from the dry vacuum pipe 1653 is againpressurized by the compressor 1654, regulated to a proper pressure bythe regulators 1661, 1662, and again supplied to the static pressurebearings of the XY-table.

As described above, the gas supplied to the static pressure bearingsmust be purified as high as possible to maximally exclude moisture andoil components, so that the turbo molecular pumps, dry pump andcompressor are required to have structures which prevent moisture andoil components from introducing into gas flow paths. It is alsoeffective to provide a cold trap, a filter or the like (1660) in themiddle of the discharge side pipe 1677 of the compressor to trapimpurities such as moisture and oil components mixed in a circulatinggas such that they are not supplied to the static pressure bearings.

In this way, since the highly pure inert gas can be circulated forreuse, the highly pure inert gas can be saved. In addition, since theinert gas is not supplied in an uncontrolled manner into a chamber inwhich the apparatus is installed, the possibility of accidents such assuffocation by the inert gas can be eliminated.

The circulating pipe system is connected to a highly pure inert gassupply system 1663 which serves to fill the highly pure inert gas intothe entire circulating system including the vacuum chamber C, vacuumpipes 1670-1675, and pressurizing pipes 1676-1680, and to supply theshortage if the flow rate of the circulating gas is reduced by somecause.

It is also possible to use a single pump as the dry vacuum pump 1653 andthe compressor 1654 by providing the dry vacuum pump 1653 with afunction of compressing to the atmospheric pressure or higher.

Further, the ultra-high vacuum pump for use in evacuating the barrel maybe implemented by a pump such as an ion pump, a getter pump instead ofthe turbo molecular pump. However, when such an entrapment vacuum pumpis used, a circulating piping system cannot be build in this portion.Also, a dry pump of another configuration such as a diaphragm dry pumpmay of course be used instead of the dry vacuum pump.

Similarly to the ninth embodiment, the tenth embodiment described withreference to FIGS. 44-46 comprises the optical system and the detectionsystem described in FIG. 43. In the tenth embodiment, the description onFIG. 43 is incorporated herewith by reference. Also, as described in theninth embodiment, When the tenth embodiment of the present invention isused in the testing process (G) or the exposure process (c) in thedevice manufacturing method described with reference to FIGS. 3 and 4(a), 4(b), miniature patterns can be stably tested or exposed at a highaccuracy, thereby making it possible to improve the yield rate ofproducts and prevent defective products from being shipped. In thisregard, the description related to FIG. 3 and FIGS. 4( a), 4(b) isincorporated herewith by reference and is omitted herein.

Embodiment Relating to Lenses in Optical System Eleventh Embodiment

An eleventh embodiment of the present invention relates to an electronbeam apparatus for evaluating patterns and so on formed on the surfaceof a sample, and a device manufacturing method for evaluating a samplein the middle of a process or at the end of the process using theelectron beam apparatus, and more particularly, to an electron beamapparatus which is capable of performing a variety of evaluations fortesting a device on a sample or the like for defects on patterns havinga minimum line width of 0.1 micron or less, CD measurement, potentialcontrast measurement, high time resolution potential measurement, and soon at a high throughput and high reliability, and a device manufacturingmethod for evaluating a sample in the middle of a process or at the endof the process using such an electron beam apparatus.

A variety of techniques have been reported on apparatuses for observinga sample including an insulating material for evaluation. Among thesetechniques, stating about a scanning electron microscope, a knownapparatus has a charging sensing function of measuring a beam current ofa primary beam, a current absorbed into a sample, the amount of electronbeam reflected from an irradiating apparatus, the amount of emittedsecondary electron beam, and so on to evaluate a charging state.

However, since the conventional scanning electron microscope asmentioned above scans a fine electron beam, i.e., a beam on the surfaceof a sample, it has a problem of significantly degraded throughput forevaluating a sample having a large area. Also, the known chargingsensing function is required to measure a variety of currents at a hightime resolution, so that the charging state cannot be correctly detectedat all times.

The eleventh embodiment of the present invention, for solving the aboveproblem, provides an electron beam apparatus which improves thestructure of lenses in an optical system to reduce the size of theoptical system; an electron beam apparatus which improves a throughputas well as improves the charging sensing function to have a higherreliability for evaluation, and a device manufacturing method which iscapable of evaluating a sample in the middle of a process or at the endof the process at a high manufacturing yield rate, using an electronbeam apparatus as mentioned above.

In the following, the eleventh embodiment of the electron beam apparatusaccording to the present invention will be described with reference tothe drawings. In FIG. 47, an electron beam apparatus 1701 comprises aprimary electron-optical system (hereinafter simply called the “primaryoptical system”) 1710, a secondary electron-optical system (hereinaftersimply called the “secondary optical system”) 1720, and a detectingsystem 1730. The primary optical system 1710, which is an optical systemfor irradiating an electron beam to the surface of an object underevaluation (hereinafter called the “sample”) S such as a wafer,comprises an electron beam source 1711 for emitting an electron beam,i.e., an electron beam; a condenser lens 1712 for converging a primaryelectron beam emitted from the electron beam source 1711; a Wien filter1715; and an objective lens 1716. These are positioned as illustrated inFIG. 48. Reference numerals 1714 and 1717 designate aligners foraligning the primary electron beam; 1718 a deflector for scanning theprimary electron beam; and 1719 an axially symmetric electrode.

The secondary optical system 1720 is positioned along an optical axiswhich is oblique with respect to the optical axis of the primary opticalsystem. Though not shown in FIG. 47, the secondary optical system maycomprise at least one lens. The detecting system 1730 comprises adetector 1731, and an image forming unit 1733 connected to the detector1731 through an amplifier 1732.

The sample S is removably supported by a holder 1741 on an XY stage 1740by a known method, and is supported by the XY stage 1740 for movementsin two orthogonal axial directions (in the left and right directions andthe direction vertical to the sheet in FIG. 47).

The electron beam apparatus 1701 comprises a retarding voltage applyingunit (hereinafter called the “applying unit”) 1750 electricallyconnected to the holder 1741; and a charging checking and landing energydetermining system (hereinafter called the “checking/determiningsystem”) 1760. The checking/determining system 1760 comprises a monitor1761 electrically connected to the image forming unit 1733; an operator1762 connected to the monitor 1761; and a CPU 1763 connected to theoperator 1762. The CPU 1763 supplies signals to the applying unit 1750and the deflector 1717.

In the eleventh embodiment, since a condenser lens 1712 is substantiallyidentical in structure to an objective lens 1716, the condenser lens1712 will be described in detail, taken as an example. The condenserlens 1712, which is an electrostatic axially symmetric lens, is formedby cutting a ceramics bulk such that an axial cross-section thereof hasa shape as shown in FIG. 47. Specifically, the condenser lens 1712includes a body 1712-1 made of ceramics. This body 1712-1 is formed witha planar shape in an annular configuration to define a circular hole1712-2 in a central portion, and the inner peripheral side ispartitioned into three plate-shaped portions 1712-3 to 1712-5 separatedin the vertical direction (the direction along the optical axis) in FIG.47. The outer periphery of the body 1712-1 made of ceramics,particularly, surroundings of the plate-shaped portions 1712-3 to 1712-5are coated with metal coating films 1712-6 to 1712-8. These coatingfilms 1712-6 to 1712-8 function as electrodes (an upper electrode1712-6, an intermediate electrode 1712-7, and a lower electrode 1712-8),respectively. The coating films, i.e., upper and lower electrodes 1712-6and 1712-8 are applied with a voltage close to the ground, while themiddle coating film, i.e., intermediate electrode 1712-7 is applied witha positive or negative high voltage having a large absolute value by anelectrode fitting 1712-9 disposed in the body 1712-1, thereby acting asa lens. Such a lens has a high working accuracy since a ceramics bulk iscut and simultaneously worked, and can be reduced in the dimension ofouter diameter.

Since the electron beam apparatus in this embodiment can reduce theouter diameter of the lens, the barrel containing the electron beamapparatus can also be reduced in the outer diameter. Therefore, for asample such as a wafer having a large diameter, a plurality of columncan be arranged for a single wafer. For example, assuming that the outerdiameter (diameter) of the lens is chosen to be 40 mm, a total of eightbarrels 1702, arranged in four in the X-direction and two in theY-direction, as illustrated in FIG. 48, can be arranged for one sample.Then, the stage (not shown), which holds the sample S, is sequentiallymoved in the Y-direction while the sample is scanned by the respectivebarrels in the X-direction for evaluation, thereby achieving athroughput seven or eight times as high as the evaluation using only oneelectron beam.

In the electron beam apparatus described above, a primary electron beam,i.e., a beam emitted from the cathode 1711-1 of the electron beam source1711 in the primary optical system 1710 is accelerated by the anode1711-2. A crossover image of the electron beam source created by theprimary electron beam is reduced by the condenser lens 1712 and theobjective lens 1716 into a thin beam of approximately 50 nm which isscanned on the sample S for irradiation. A secondary electron beamemitted from the sample by the irradiation of the primary electron beamis attracted by the axially symmetric electrode 1719 toward theobjective lens. As the secondary electron beam is passed toward theobjective lens 1716 or returned to the sample side by the axiallysymmetric electrode 1719, a potential contrast can be produced for asample pattern.

The secondary electron beam passing through the objective lens isseparated from the primary optical system 1710 by the Wien filter 1715,introduced into the secondary electron-optical system (hereinaftersimply called the “secondary optical system”) 1720, and detected by thedetector 1731 in the detecting system 1730. The detector 1731 transducesthe detected secondary electron beam image into an electric signalindicative of the intensity thereof. The electric signal output fromeach detector in this way is amplified by the corresponding amplifier1732, input to the image forming unit 1733, and converted into imagedata in this image forming unit. Since the image forming unit 1733 isfurther supplied with a scanning signal for deflecting the primaryelectron beam, the image forming unit displays an image which representsthe surface of the sample S. By comparing this image with a referencepattern, defects on the sample S can be detected. While this embodimentuses a single electron beam, a plurality of beams may be preferred tothe single beam in view of an improvement in throughput.

The image data converted by the image forming unit 1733 is displayed asan image by the display device 1761 of the checking/determiningapparatus 1760, and the image is evaluated by the operator 1762. Theoperator 1762 executes a charging checking function in this embodiment.Also, the operator 1762 can check a charge-up state based on the image.Then, the result is input to the CPU 1763, and a landing energy is setto an optimal value. The CPU 1763 constitutes a landing energydetermining unit in this embodiment.

More specifically, as shown in FIG. 49[A], evaluation is made on alocation of a sample under evaluation vulnerable to the influence ofcharging, i.e., a corner region of a memory cell 1771 in a chip 1770formed on the surface of a wafer as a sample. Specifically, (1) theamounts of distortions in patterns 1773, 1774 are measured on a memorycell boundary 1772 in the corner region, or (2) the contrasts of signalstrengths produced when the corner region of the memory cell was scannedso as to cross the pattern (as indicated by arrows A1 and A2) may bedisplayed as solid lines 1775 and 1777 in FIG. 49[B], for comparisonwith contrasts 1776 and 1778 (both indicated by broken lines in FIG.49[B]) of signal strengths produced when patterns were scanned alongarrows A3, A4 in a central region of the chip.

The retarding voltage applying unit 1750 was applied with a plurality ofvalues of voltages, and the amounts of distortions 1773 and 1774 or thecontrasts 1775, 1777 and 1776, 1778 were measured each time a voltagewas applied. A less amount of distortion 1773, 1774 is evaluated asbeing less affected by the charge-up. Also, the value of contrast 1775,1777 in the corner region closer to the value of contrast in the centralregion is evaluated as being less affected by the charge-up.

When a retarding voltage is found with a satisfactory charge-up state,this value is applied to the applying unit 1750 through the CPU 1763, orif values of optimal beam currents are found, the sample or wafer isevaluated with these values.

The eleventh embodiment of the present invention can be used in thetesting process (G) in the device manufacturing method described withreference to FIGS. 3 and 4( a), 4(b). In this way, semiconductor deviceseven having fine patterns can be tested at a high throughput, so that atotal inspection can also be conducted, thereby making it possible toimprove the yield rate of products and prevent defective products frombeing shipped. In this regard, the description related to FIG. 3 andFIGS. 4( a), 4(b) is incorporated herewith by reference and is omittedherein.

Embodiment Relating to Detection of Defects Twelfth Embodiment

A twelfth embodiment of the present invention relates to a defecttesting apparatus for testing a sample such as a semiconductor wafer fordefects by comparing an image of the sample with a previously preparedreference image, and a semiconductor device manufacturing method formanufacturing semiconductor devices using such a defect testingapparatus.

Conventionally, a defect testing apparatus has been utilized insemiconductor manufacturing processes and so on for testing a samplesuch as a semiconductor wafer for defects by detecting a secondaryelectron beam generated by irradiating the sample with a primaryelectron beam. Such a defect testing apparatus involves a techniquewhich applies an image recognition technique to automate the testing fordefects and improve the efficiency thereof. This technique causes acomputer to match pattern image data of a region under testing on thesurface of a sample acquired by detecting a secondary electron withpreviously stored reference image data of the surface of the sample toautomatically determine the presence or absence of defects on the samplebased on the result of processing.

Recently, increasingly higher definitions are required for patterns,particularly in the field of semiconductor manufacturing, so that theneed for detecting fine defects has been increased. Under such acircumstance, a further improvement in recognition accuracy is requiredas well for the defect testing apparatus which applies the imagerecognition technique as mentioned above.

However, the aforementioned prior art experiences a problem ofdiscrepancy in position between an image of a secondary electron beamcaptured by irradiating a primary electron beam to a region undertesting on the surface of the sample and a previously prepared referenceimage to degrade the accuracy of detecting defects. This discrepancy inposition constitutes a grave problem particularly when an irradiatingarea of the primary electron beam shifts with respect to the wafer sothat a portion of a pattern under testing is lost from a detected imageof the secondary electron beam. This problem cannot be addressed only bya technique for simply optimizing a matching region within a detectedimage (see Japanese Patent Publication No. 6-95340). This can be acritical disadvantage, particularly, in testing for high definitionpatterns.

The twelfth embodiment of the present invention, to solve the problemmentioned above, provides a defect testing apparatus for preventing adegraded defect testing accuracy due to the discrepancy in positionbetween an image under testing and a reference image; and asemiconductor manufacturing method for improving the yield rate fordevice products and preventing defective products from being shipped bytesting a sample for defects using a defect testing apparatus asmentioned above in a semiconductor device manufacturing process.

FIG. 50 illustrates a general configuration of the defect testingapparatus according to the twelfth embodiment of the present invention.This defect testing apparatus comprises an electron beam source 1801 foremitting a primary electron beam; an electrostatic lens 1802 fordeflecting and reshaping the emitted primary electron beam; a Wienfilter 1803 for deflecting the reshaped primary electron beam in a fieldin which an electric field E and a magnetic field B are orthogonal toeach other such that the primary electron beam impinges substantiallyperpendicularly to a semiconductor wafer 1805; an objective lens 1810for focusing the deflected primary electron beam on the wafer 1805; astage 1804 disposed in a sample chamber, not shown, which can beevacuated to vacuum and is movable in a horizontal plane with the wafer1805 carried thereon; an electrostatic lens 21806 of a image projectionsystem for imaging and projecting a secondary electron beam emitted fromthe wafer 1805 by the irradiation of the primary electron beam and/or areflected electron beam at a predetermined magnification to form animage; detector 1807 for detecting the formed image as a secondaryelectron beam image of the wafer; and a controller 1816 for controllingthe overall apparatus and executing the processing for detecting defectson the wafer 1805 based on the secondary electron beam image detected bythe detector 1807. The secondary electron beam image includes acontribution by reflected electrons as well as a contribution by thesecondary electron beam.

In addition, between the objective lens 1810 and the wafer 1805, adeflecting electrode 1811 is interposed for deflecting an incident angleof the primary electron beam to the wafer 1805 by an electric field orthe like. The deflecting electrode 1811 is connected to a deflectioncontroller 1812 for controlling the electric field of the deflectingelectrode. This deflection controller 1812 is connected to thecontroller 1816 to control the deflecting electrode to generate anelectric field in response to an instruction from the controller 1816 bythe deflecting electrode 1811. The deflection controller 1812 can beimplemented as a voltage controller for controlling a voltage applied tothe deflecting electrode 1811.

The detector 1807 may be in an arbitrary configuration as long as it cantransduce a secondary electron beam image formed by the electrostaticlens 1806 into a signal available for post-processing. For example, asillustrated in detail in FIG. 55, the detector 1807 comprises amulti-channel plate 1850; a fluorescent screen 1852; a relay lens 1854;and an imager sensor 1856 comprised of a large number of CCD devices.The multi-channel plate 1850 comprises a large number of channels withinthe plate to generate a larger number of electrons while the secondaryelectrons focused by the electrostatic lens 1806 pass through thechannels. In other words, the secondary electron beam is amplified. Thefluorescent screen 1852 generates fluorescent light by the amplifiedsecondary electron beam to transduce the secondary electron beam intolight. The relay lens 1854 introduces this fluorescent light into theCCD imager sensor 1856, and the CCD imager sensor 1856 converts anintensity distribution of secondary electrons on the surface of thewafer 1805 into an electric signal per device, i.e., digital imagesignal which is output to the controller 1816.

As illustrated in FIG. 50, the controller 1816 may comprise ageneral-purpose personal computer or the like. This computer comprises acontroller body 1814 for executing a variety of control and operationalprocessing in accordance with predetermined programs; a CRT 1815 fordisplaying results of processing by the body 1814; and an input device1818 such as a keyboard and a mouse for the operator to enterinstructions. Of course, the controller 1816 may be built by hardwarededicated to the defect testing apparatus, a workstation, or the like.

The controller body 1814 comprises a CPU, RAM, ROM, a hard disk, all notshown, a variety of control boards such as a video board, and so on. Ona memory such as RAM and hard disk, a secondary electron beam imagestorage region 1808 is allocated for storing an electric signal receivedfrom the detector 1807, i.e., digital image data representing asecondary electron beam image of the wafer 1805. Also, on the hard disk,a reference image storage 1813 exists for previously storing referenceimage data of the wafer which is free from defects. Further, the harddisk stores a defect detecting program 1809 for reading the secondaryelectron beam image data from the storage region 1808 to automaticallydetect defects on the wafer 1805 in accordance with a predeterminedalgorithm based on the image data, in addition to a control program forcontrolling the overall defect testing apparatus. This defect detectingprogram 1809, details of which will be described later, has functions ofmatching a reference image read from the reference image storage 1813with an actually detected secondary electron beam image to automaticallydetect a defective portion, and displaying a warning to the operatorupon determining that defects are found. In this event, a secondaryexcessive current generated image 1817 may be displayed on a displayscreen of the CRT 1815.

Next, the action of the defect testing apparatus illustrated in FIG. 50will be described, by way of example, with reference to flow chartsillustrated in FIGS. 52-54. First, as illustrated in a flow of a mainroutine of FIG. 52, the wafer 1805, under testing, is set on the stage1804 (step 1900). This may be in a manner in which a large number ofwafers 1805 stored in a loader, not shown, are automatically set one byone on the stage 1804.

Next, each of a plurality of images of regions under testing, partiallyoverlapping and displaced from one another on the XY plane of thesurface of the wafer 1805 is captured (step 1904). The plurality ofregions under testing, the images of which should be captured, refer torectangular regions designated by reference numerals 1832 a, 1832 b, . .. , 1832 k, . . . , for example, on the surface 1834 under testing ofthe wafer, as illustrated in FIG. 56. It can be seen that these areshifted in position, while partially overlapping, about a testingpattern 1830 of the wafer. For example, as illustrated in FIG. 51, 16images 1832 (images under testing) in the regions under testing arecaptured. Here, in the images illustrated in FIG. 51, a rectangular cellcorresponds to one pixel (alternatively, may be a block unit larger thana pixel), wherein a black painted cell corresponds to an image portionof the pattern on the wafer 1805. Details on this step 1904 will bedescribed later with reference to a flow chart of FIG. 53.

Next, the image data of the plurality of regions under testing capturedat step 1904 is compared one by one with the reference image data storedin the storage 1813 (step 1908 in FIG. 52) to determine whether or notany defect is found on the tested surface of the wafer covered by theplurality of regions under testing. In this step, so-called matchingbetween image data is executed, details of which will be described laterwith reference to a flow chart of FIG. 54.

If it is determined from the result of comparison at step 1908 that anydefect is found on the tested surface of the wafer covered by theplurality of regions under testing (determined as affirmative at step1912), the existence of defect is warned to the operator (step 1918). Asa method of warning, for example, a message notifying the existence ofdefect may be displayed on the display screen of the CRT 1815, or anenlarged image 1817 of the pattern including the defect may be displayedsimultaneously with this. Such a defective wafer may be immediatelyremoved from the sample chamber 1803, and stored in another storageplace separately from defect-free wafers (step 1919).

If it is determined as the result of comparison at step 1908 that thewafer 1805 is free of defect (determined as negative at step 1912), itis determined whether or not more regions to be tested still remain onthe wafer 1805 currently under testing (step 1914). If any region to betested remains (determined as affirmative at step 1914), the stage 1804is driven to move the wafer 1805 such that another region to be testedfrom now on enters the irradiating region of the primary electron beam(step 1916). Subsequently, the flow returns to step 1902, from whichsimilar processing is repeated for the other region under testing.

If no region to be tested remains (determined as negative at step 1914),or after a defective wafer removing step (step 1919), it is determinedwhether or not the wafer 1805 currently under testing is the last wafer,i.e., whether or not untested wafers remain in the loader, not shown(step 1920). If not the last wafer (determined as negative at step1920), the tested wafer is stored in a predetermined storage place, anda new untested wafer is set on the stage 1804 instead (step 1922).Subsequently, the flow returns to step 1902, from which similarprocessing is performed on this wafer. If the last wafer (determined asaffirmative at step 1920), the tested wafer is stored in a predeterminedstorage place, followed by termination of the while process.

Next, a flow of the processing at step 1904 will be described along aflow chart of FIG. 53. In FIG. 53, an image number i is first set to aninitial value 1 (step 1930). This image number is an identificationnumber sequentially allocated to each of the plurality of image regionsunder testing. Next, an image position (X_(i), Y_(i)) is determined fora region under testing designated the set image number i (step 1932).This image position is defined as a particular position in the region,for example, a central position in the region for defining a regionunder testing. At the present time, since i=1, the image position isindicated by (X₁, Y₁) which corresponds to the central position of theregion under testing 1832 a illustrated in FIG. 16, by way of example.The image positions of all image regions under testing have beenpreviously determined and stored, for example, on the hard disk in thecontroller 1816 from which it is read at step 1932.

Next, the deflection controller 1812 applies a potential to thedeflecting electrode 1811 such that the primary electron beam passingthrough the deflecting electrode 1811 in FIG. 50 is irradiated to animage region under testing at the image position (X_(i), Y_(i))determined at step 1932 (step 1934 in FIG. 53). Next, a primary electronbeam is emitted from an electron beam source 2501, passes through theelectrostatic lens 1802, Wien filter 1803, objective lens 1810 anddeflecting electrode 1811, and is irradiated on the surface of the setwafer 1805 (step 1936). In this event, the primary electron beam isdeflected by an electric field created by the deflecting electrode 1811,and is irradiated over the entire image region under testing at theimage position (X_(i), Y_(i)) on the surface 1834 under testing of thewafer. When the image number i=1, a region under testing is indicated by1832 a.

From the region under testing irradiated with the primary electron beam,a secondary electron beam and/or a reflected electron beam (hereinafter,the two are collectively called the “secondary electron beam”) areemitted. Then, the generated secondary electron beam is focused on thedetector 1807 at a predetermined magnification provided by theelectrostatic lens 1806 in the enlargement projection system. Thedetector 1807 detects the focused secondary electron beam, andtransduces it into an electric signal per detector device, i.e., digitalimage data which is then output (step 1938). Next, the detected digitalimage data designated the image number i is transferred to the secondaryelectron beam image storage region 1808 (step 1940).

Next, the image number i is incremented by one (step 1942), and it isdetermined whether or not the incremented image number (i+1) exceeds aconstant value i_(MAX) (step 1944). This i_(MAX) indicates the number ofimage under testing to be captured, and is “16” in the aforementionedexample of FIG. 51.

If the image number i does not exceed the constant value i_(MAX)(determined as negative at step 1944), the flow returns again to step1932, where an image position (X_(i+1), Y_(i+1)) is again determined forthe incremented image number (i+1). This image position indicates aposition shifted from the image position (X_(i), Y_(i)) determined inthe preceding routine by a predetermined distance (ΔX_(i), ΔY_(i)) inthe X-direction and/or Y-direction. In the example of FIG. 56, theregion under testing is located at a position (X₂, Y₂) shifted from (X₁,Y₁) only in the Y-direction, and covers a rectangular region 1832 bindicated by a broken line. The values (ΔX_(i), ΔY_(i)) (i=1, 2, . . . ,i_(MAX)) can have been empirically determined as appropriate from dataon how much the pattern 1830 on the surface 1834 under testing of thewafer actually shifts from the field of view of the detector 1807, andthe number and area of regions under testing.

Then, the processing at steps 1932-1942 is repeatedly executed insequence for i_(MAX) regions under testing. As illustrated in FIG. 56,these regions under testing are shifted in position, while partiallyoverlapping, on the surface 1834 under testing of the wafer, such thatan image position (X_(k), Y_(k)) after shifted k times indicates animage region under testing 1832 k. In this way, 16 image data undertesting illustrated in FIG. 51 are stored in the image storage region1808. It can be seen that the plurality of captured images 1832 (imagesunder testing) of the plurality of regions under testing have partiallyor completely captured over the image 1830 a of the pattern 1830 on thesurface 1834 under testing on the wafer, as illustrated in FIG. 56.

If the incremented image number i exceeds i_(MAX) (determined asaffirmative at step 1944), this subroutine is returned to proceed to thecomparison step (step 1908) in the main routine of FIG. 52.

The image data transferred to the memory at step 1940 is comprised ofthe intensity value (so-called beta data) of secondary electrons perpixel detected by the detector 1807. For matching with the referenceimage at the later comparison step (step 1908 in FIG. 52), they may bestored in a storage region 8 after applied with a variety of operationalprocessing. Such operational processing includes, for example,normalization for fitting the size and/or concentration of image data tothe size and/or concentration of reference image data; processing forremoving a group of isolated pixels below a predetermined number ofpixels as noise; and so on. Further, rather than simple unprocesseddata, image data may have been compress converted into a feature matrixwhich extracts features of a detected pattern to the extent of avoidinga degradation in the detection accuracy of the high definition pattern.Such a feature matrix may be an m×n feature matrix or the like, whichhas a total sum of secondary electron beam intensity values of pixelsincluded in each of m×n blocks (m<M, n<N) divided, for example, from atwo-dimensional region under testing comprised of M×pixels (or anormalized value derived by dividing the total sum value by the totalnumber of pixels over the entire region under testing) as each matrixcomponent. In this event, the reference image data is stored in the samerepresentation as well. The image data referred to in the eleventhembodiment encompasses feature extracted image data by an arbitraryalgorithm in this manner, not mention to simple unprocessed data.

Next, a flow of the processing at step 1908 will be described along aflow chart of FIG. 54. First, the CPU in the controller 1816 reads thereference image data from the reference image storage 1813 (FIG. 50)onto a working memory such as RAM (step 1950). This reference image isdesignated by reference numeral 1836 in FIG. 51. Then, the image numberi is reset to 1 (step 1952), and image data under testing designated theimage number i is read onto the working memory from the storage region1808 (step 1954).

Next, the read reference image data is matched with data of an image ito calculate a distance value D_(i) between both (step 1956). Thisdistance value D_(i) represents the similarity between the referenceimage and the image i under testing, and a larger distance valueindicates a larger difference between the reference image and the imageunder testing. Any arbitrary value may be employed as the distance valueD_(i) as long as it is an amount representative of the similarity. Forexample, when image data is comprised of M×N pixels, a secondaryelectron beam intensity (or feature amount) of each pixel is regarded aseach position vector component of an M×N-dimensional space, and aEuclidean distance or correlation coefficient may be calculated betweena reference image vector and a vector of the image i on thisM×N-dimensional space. Of course, a distance other than the Euclideandistance, for example, a so-called urban distance or the like may becalculated. Further, as a large number of pixels require an immenseamount of operations, the distance value between respective image datarepresented by m×n feature vectors may be calculated as described above.

Next, it is determined whether or not the calculated distance valueD_(i) is smaller than a predetermined threshold Th (step 1958). Thethreshold Th can be empirically found as a reference for determiningsufficient matching between the reference image and an image undertesting.

If the distance value D_(i) is smaller than the predetermined thresholdTh (determined as affirmative at step 1958), “non-defective” isdetermined for the tested surface 1834 on the wafer 1805 (step 1960),followed by returning the subroutine. Specifically, “non-defective” isdetermined if any one of images under testing substantially matches thereference image. In this way, all images under testing need not bematched with the reference image, so that the determination can be madeat a high speed. In the example of FIG. 51, it can be seen that an imageunder testing at the third row, third column substantially matches thereference image without discrepancy in position.

If the distance value D_(i) is equal to or larger than the predeterminedthreshold Th (determined as negative at step 1958), the image number iis incremented by one (step 1962), ad it is determined whether or notthe incremented image number (i+1) exceeds the constant value i_(MAX)(step 1964). If the image number i does not exceed the constant valuei_(MAX) (determined as negative at step 1964), the flow again returns tostep 1954, where image data designated by the incremented image number(i+1) is read, and similar processing is repeated.

If the image number i exceeds the constant value i_(MAX) (determined asaffirmative at step 1964), “defective” is determined for the surface1834 under testing on the wafer 1805 (step 1966), followed by returningthe subroutine. Specifically, “defective” is determined unless allimages under testing substantially match the reference image.

The defect testing apparatus according to the twelfth embodiment of thepresent invention can be used in the testing process (G) in the devicemanufacturing method described with reference to FIGS. 3 and 4( a),4(b). In this event, semiconductor devices even having fine patterns canbe tested for defects at a high accuracy without image fault on thesecondary electron image, thereby making it possible to improve theyield rate of products and prevent defective products from beingshipped. In this regard, the description related to FIG. 3 and FIGS. 4(a), 4(b) is incorporated herewith by reference and is omitted herein.

The twelfth embodiment of the present invention is not limited to thoseitems so far described, but may be arbitrarily modified. For example,while the semiconductor device 1805 has been presented as an example ofa sample under testing, samples under testing directed by the presentinvention are not limited thereto, but any arbitrary one can be selectedas long as defects thereon can be detected by an electron beam. Forexample, a mask formed with a pattern for exposure to a wafer, and so onmay be subjected to the testing.

Also, the twelfth embodiment of the present invention can be applied toan arbitrary apparatus which can capture an image which can be testedfor defects on a sample.

Further, the deflecting electrode 1811 can be placed at an arbitraryposition, not limited to the position between the objective lens 1810and the wafer, as long as it can change an irradiating region of theprimary electron beam. For example, it may be placed between the Wienfilter 1803 and the objective lens 1810, between the electron beamsource 1801 and the Wien filter 1803, and so on. Furthermore, thedeflecting direction may be controlled by controlling the fieldgenerated by the Wien filter 1803. In other words, the Wien filter 1803may be provided with the function of the deflecting electrode 1811.

Also, when image data are matched in the twelfth embodiment, eitherpixels or feature vectors are matched. Alternatively, both may becombined. For example, a high speed matching is conducted with featurevectors which require a less amount of operations, and as a result, foran image under testing exhibiting a high similarity, more detailed pixeldata are matched. By such two-step processing, a high speed and accuracycan be simultaneously provided.

Also, in the twelfth embodiment of the present invention, discrepancy inposition of an image under testing is accommodated only by shifting theposition of the irradiating region of the primary electron beam.Alternatively, it is also possible to combine the processing forsearching image data for an optimal matching region thereon (forexample, regions having high correlation coefficients are detected formatching) with the present invention before or during the matching. Inthis way, large discrepancy in position of an image under testing can beaccommodated by shifting the irradiating region of the primary electronbeam in accordance with the present invention, while relatively smalldiscrepancy in position can be absorbed by the digital image processingat a later step, thereby making it possible to improve the accuracy indetecting defects.

Further, while the configuration in FIG. 50 has been illustrated as theelectron beam apparatus for testing for defects, the electron-opticalsystem and so on can be arbitrarily modified. For example, while theelectron beam irradiating means (1801, 1802, 1803) of the illustrateddefect detecting apparatus is of the type that directs the primaryelectron beam to the surface of the wafer 1805 vertically from above,the Wien filter 1803 may be omitted so that the primary electron beam isdirected obliquely to the surface of the wafer 1805.

Also, the processing according to the flow chart of FIG. 52 is notlimited to that described in the figure. For example, while a sampledetermined as defective at step 1912 is not subjected to the testing ofthe remaining regions for defects, the flow of the processing may bechanged to detect defects over the entire region. Also, if the entiretested region of a sample can be covered by one irradiation by expandingthe irradiating region of the primary electron beam, step 1914 and step1916 may be omitted.

While the first embodiment through twelfth embodiment of the presentinvention have been described in detail, a term “predetermined voltage”is assumed to mean a voltage at which a measurement such as testing isconducted in any embodiment.

Also, while a variety of embodiments so far described employ electronbeams as charge particle beams, the present invention is not limited tothis, but charged particle beams other than electron beams, andnon-charged particle beams such as neutron having no charge, laserlight, and electromagnetic waves may be used.

As the charged particle beam apparatus according to the presentinvention operates, a target object floats and is attracted to a highvoltage region by a proximity interaction (charging of particles near asurface), so that organic substances are deposited on a variety ofelectrodes used for formation and deflection of charged particle beams.The organic substance gradually deposited by the charged surfaceadversely affects the mechanisms for forming and deflecting the chargedparticle beams, so that such a deposited organic substance must beperiodically removed. Here, for periodically removing the depositedorganic substance, preferably, an electrode near a region on which theorganic substance is deposited is utilized to create a plasma ofhydrogen, oxygen or fluorine, and substitutes including them such as HF,H₂O, CMFN in a vacuum to maintain a plasma potential within the space ata potential at which the sputtering occurs on the surface of theelectrode (several kV, for example 20V-5 kV) to remove only the organicsubstance through oxidization, hydrogenization and fluoridization.

INDUSTRIAL AVAILABILITY

As will be understood from the first embodiment, the present inventioncan significantly improve the throughput as compared with the prior artby providing a testing apparatus based on a charge particle beam.

As will be understood from the second embodiment, the present inventionproduces distinct effects as follows.

1. The general configuration can be established for a testing apparatusin accordance with an electron beam based imaging projection schemeusing charged particle beams, which can process objects under testing ata high throughput.

2. A clean gas is forced to flow to an object under testing within themini-environment chamber to prevent dust from attaching to the objectunder testing, and a sensor is provided for observing the cleanliness,thereby making it possible to test the object under testing whilemonitoring dust within the space.

3. Since the loading chamber and the working chamber are integrallysupported through a vibration isolator, an object under testing can besupplied to the stage device and tested thereon without affected by theexternal environment.

4. Since the precharge unit is provided, a wafer made of an insulatingmaterial will not either be affected by charging.

As will be understood from the third embodiment, the present inventionproduces distinct effects as follow.

1. Since the charged particle beam source is separated from theelectron-optical system by a partition wall, a required degree of vacuumcan be achieved independently for each section.

2. Since the charged particle beam source is coupled to theelectron-optical system through holes of small conductance, a largepressure difference can be taken between the charged particle beamsource and the electron-optical system.

3. Since the partition wall is formed with holes at positions away fromthe optical axes of the respective charged particle beam sources, evenif positive ions return along the optical axis from the sample or theelectron-optical system to the cathode of the charged particle beamsource, they are blocked by the partition wall, so that the cathode willnot be damaged by positive ions.

As will be understood from the fourth embodiment, the present inventionproduces distinct effects as follows.

1. Since the electrodes or portions of the electrodes are coated with ametal having a work function of 5 eV or higher, secondary chargedparticle beam will hardly be emitted from the electrodes, so that adischarge is less likely to occur between electrodes, and a breakdownbetween electrodes is reduced.

2. Since the electrodes or portions of the electrodes are coated withplatinum (work function: 5.3 [eV]) or an alloy which contains platinumas a main material, secondary charged particle beam will hardly beemitted from the electrodes, so that a discharge is less likely to occurbetween electrodes, and a breakdown between electrodes is reduced.

3. Even if the sample is a semiconductor wafer, attachment of platinumcoated on the electrodes onto a pattern of the semiconductor wafer, ifany, would not deteriorate the performance of a resulting device, sothat the present invention is preferable for testing a semiconductorwafer.

4. The electrodes are supported by an insulating material, so that adischarge between electrodes, and hence a breakdown between electrodeshardly occur.

5. At least one of electrodes is shaped to have a step between a firstelectrode surface and a second electrode surface and these electrodesurfaces, so that the surface of the insulating material need not beformed with crimps, resulting in a lower manufacturing cost.

6. Since the minimum creeping distance of the insulating materialbetween electrodes is substantially equal to the distance betweenelectrodes in a supported electrode portion, the surface of theinsulating material is substantially free from ruggedness between theelectrodes, and a gas exhausted from the insulating material will not beincreased, so that the degree of vacuum will not be lowered in a beampath of the apparatus.

As will be understood from the fifth embodiment, the present inventionproduces a distinct effect in that the influence of chromatism producedby the ExB separator can be reduced due to an energy distribution of theprimary charged particle beam or second charged particle beam.

As will be understood from the sixth embodiment, the present inventionproduces distinct effects as follows.

1. Since no optical sensor is required for measuring the level of thesurface of a sample, the designing can be optimally accomplished betweenthe objective lens and the sample only with the electron-optical system.

2. Since the charge particle beam scanning/detecting system can befocused only by adjusting a low voltage, a settling time can be reduced.In other words, the focusing can be performed in a short time.

3. Astigmatism can also be corrected in a short time during the focusingoperation as required.

4. Since a sample in the middle of a process can be evaluated in a shorttime, it is possible to increase the yield rate of the devicemanufacturing.

As will be understood from the seventh embodiment, the present inventionproduces distinct effects as follows.

1. A piezoelectric element is attached to a mechanical construction suchthat it receives a force from vibrations of the mechanical construction,and a vibration attenuating circuit is electrically connected to thepiezoelectric element for attenuating electric energy output from thepiezoelectric element, so that unwanted vibrations due to the resonanceof the construction for aligning the beam can be appropriatelyattenuated so as to highly accurately maintain the alignment of the beamwithout necessarily increasing the rigidity of the construction.

2. It is therefore possible to realize mitigation of constraints on thedesign, reduction in size and weight of the apparatus, and improvementon the economy.

3. Highly efficient manufacturing, testing, working, observation and soon of semiconductor devices can be achieved by using the chargedparticle beam apparatus as described above in a semiconductor devicemanufacturing process.

As will be understood from the eighth embodiment, the present inventionproduces distinct effects as follows.

1. By an electrostatic chuck and a combination of a wafer and theelectrostatic chuck, a voltage required to suck and hold the wafer isapplied associated with a voltage applied to the wafer, so that thewafer can be sucked and held without fail until the wafer has beentested.

2. Even with a wafer centrally bowed in concave toward the electrostaticchuck, the front surface of the wafer can be securely sucked and held.Also, a discharge imprint formed on the wafer is reduced to a minimallyrequired size, and an extremely small amount of particles occur during adischarge.

3. By using the electrostatic chuck of the present invention and acombination of a wafer and the electrostatic chuck in a devicemanufacturing method to securely suck and hold the wafer on theelectrostatic chuck on a moving stand during testing, semiconductordevices even having fine patterns can be tested at a high throughput, sothat a total inspection can also be conducted, thereby making itpossible to improve the yield rate of products and prevent defectiveproducts from being shipped.

As will be understood from the ninth embodiment, the present inventionproduces distinct effects as follows.

1. The stage device can demonstrate highly accurate positioningperformance in vacuum, and the pressure at a charged particle beamirradiated position is hardly increased. In other words, a sample can behighly accurately processed by a charged particle beam;

2. A gas released from the static pressure bearings can hardly passthrough the partition into the charged particle beam irradiating region.This can further stabilize the degree of vacuum at the charged particlebeam irradiated position.

3. An exhausted gas is difficult to pass to the charge particle beamirradiating region, thereby facilitating to stably hold the degree ofvacuum at the charged particle beam irradiated position.

4. The vacuum chamber is divided into the charged particle beamirradiation chamber, a static pressure bearing chamber, and anintermediate chamber through a small conductance, and a vacuumevacuation system is configured to set lower pressures from the chargedparticle beam irradiation chamber to intermediate chamber and to staticpressure bearing chamber in this order, fluctuations in pressure to theintermediate chamber are suppressed by the partition, while fluctuationsin pressure to the charge particle beam irradiation chamber is furtherreduced by another partition, thereby making it possible to reduce thefluctuations in pressure to a level at which substantially no problemarises.

5. An increase in pressure can be suppressed when the stage is moved;

6. An increase in pressure can be further suppressed to when the stageis moved.

7. Since a testing apparatus which provides highly accurate stagepositioning performance and a stable degree of vacuum in a chargedparticle beam irradiating region can be realized, it is possible toprovide a testing apparatus which is high in testing performance andfree from fear of contaminating the sample.

8. Since an exposure apparatus which provides highly accurate stagepositioning performance and a stable degree of vacuum in a chargedparticle beam irradiating region can be realized, it is possible toprovide an exposure apparatus which is high in exposure accuracy andfree from fear of contaminating the sample.

9. Fine semiconductor circuits can be formed by manufacturingsemiconductors using an apparatus which provides highly accurate stagepositioning performance and a stable degree of vacuum in a chargedparticle beam irradiating region.

As will be understood from the tenth embodiment, the present inventionproduces distinct effects as follows.

1. A sample on the stage can be stably processed by means of a chargedparticle beam using the stage having a similar structure to a staticpressure bearing type stage which is generally used in the atmosphere (astatic pressure bearing stage having no differential pumping mechanism).

2. The influence on the degree of vacuum in the charge particle beamirradiating region can be minimized, so that the sample can be stablyprocessed by means of the charged particle beam;

3. It is possible to provide a testing apparatus which provides highlyaccurate stage positioning performance and a stable degree of vacuum ina charged particle beam irradiating region;

4. It is possible to provide an exposure apparatus which provides highlyaccurate stage positioning performance and a stable degree of vacuum ina charged particle beam irradiating region; and

5. Fine semiconductor circuits can be formed by manufacturingsemiconductors using an apparatus which provides highly accurate stagepositioning performance and a stable degree of vacuum in a chargedparticle beam irradiating region.

As will be understood from the eleventh embodiment, the presentinvention produces distinct effects as follows:

1. The throughput can be improved by an integer multiple proportional tothe number of optical systems.

2. Highly reliable evaluation can be made since a wafer is evaluatedwith the least charging state.

3. Since the charging performance is not evaluated by measuring avariety of currents but with actual images, more correct evaluationresults can be provided.

As will be understood from the twelfth embodiment, the present inventionproduces distinct effects as follows.

1. Since a sample is tested for defects by capturing each of images of aplurality of regions under testing on the sample which are displacedfrom one another while partially overlapping, and comparing these imagesof the regions under testing with a reference image, it is possible toprevent a degraded defect testing accuracy due to discrepancy inposition between the images under testing and the reference image.

2. Since a sample is tested for defects using the defect testingapparatus as described above, it is possible to improve the yield rateof products and prevent defective products from being shipped.

1. A beam application apparatus for conducting at least one of theworking, manufacturing, observing and testing of a material byirradiating the material with a beam, comprising: a mechanical structurefor determining a location of the beam relative to the material; apiezoelectric element mounted to the mechanical structure to receive aforce due to a vibration of the mechanical structure; a vibrationattenuating circuit electrically connected to the piezoelectric elementfor attenuating an electric energy produced by the piezoelectricelement.
 2. A beam application apparatus as claimed in claim 1, whereinthe vibration attenuating circuit comprises at least an inductance orinductive means as an equivalent circuit of the inductance, wherein theinductive means and the piezoelectric element having an electrostaticcapacitance form a resonance circuit, and wherein an inductance of theinductive means is determined relative to the electrostatic capacitanceof the piezoelectric element so that a resonance frequency of theresonance circuit is substantially the same as that of the mechanicalstructure.
 3. A beam application apparatus as claimed in claim 2,wherein the vibration attenuating circuit further comprises a resistanceelement.
 4. A semiconductor manufacturing process having steps ofconducting at least one of the working of a semiconductor device, themanufacturing of the semiconductor device, the observing a worked orfinished semiconductor device and the testing of the worked or finishedsemiconductor device, by using a beam application apparatus as claimedin claim
 1. 5. A vibration suppressing method of attenuating amechanical vibration of a beam application apparatus for conducting atleast one of the working, manufacturing, observing and testing of amaterial by irradiating the material with a beam, comprising the stepsof: providing a piezoelectric element to receive a force from themechanical vibration: and forming a resonance circuit by connecting, tothe piezoelectric element having an electrostatic capacitance, at leastan element having an inductance or inductive means as an equivalentcircuit of the element, wherein an inductance of the inductive means isdetermined relative to the electrostatic capacitance of thepiezoelectric element so that a resonance frequency of the resonancecircuit is substantially the same as that of the mechanical structure.6. A semiconductor manufacturing process having steps of conducting atleast one of the working of a semiconductor device, the manufacturing ofthe semiconductor device, the observing a worked or finishedsemiconductor device and the testing of the worked or finishedsemiconductor device, by using a beam application apparatus as claimedin claim
 2. 7. A semiconductor manufacturing process having steps ofconducting at least one of the working of a semiconductor device, themanufacturing of the semiconductor device, the observing a worked orfinished semiconductor device and the testing of the worked or finishedsemiconductor device, by using a beam application apparatus as claimedin claim 3.